6.1.1 Freedom of the Seas

The ocean has traditionally been divided into two legal regimes: territorial waters, where the coastal State has sovereignty, and the high seas, which is dominated by the principles of freedom and the exclusivity of flag State jurisdiction.Footnote ³ The freedom of the high seas, as a rule of customary law as well as treaty law, is a cornerstone of the international law of the sea.Footnote ⁴ Although its meaning and content have undergone change and refinement over time, the freedom of the high seas has traditionally included the freedom to conduct military activities in times of both peace and war, either defensive or offensive.Footnote ⁵ In theory, subject to the principle of peaceful purposes, the high seas can be used by all ships and aircraft for activities that are not explicitly prohibited under customary or conventional international law.Footnote ⁶

Broadly speaking, military uses of the sea embrace a wide and complex range of peacekeeping and wartime activities conducted not only on the water surface and in the column, on the seabed and subsoil but also in superjacent air space, by warships, support vessels, military aircraft and tactical and ballistic missile submarines.Footnote ⁷ In addition, military uses of the sea include cyber operations conducted from or through cyber infrastructure located in seas, including infrastructure mounted on ships and submarines, aircraft above the seas, offshore installations and through submarine communication cables.Footnote ⁸ The military uses of the sea serve a variety of purposes for governments.Footnote ⁹ First, in order to protect a State’s interests at sea, warships and military aircraft commonly conduct manoeuvres at sea to maintain readiness of engagement, with or without weapons testing.Footnote ¹⁰ Second, duly authorised government entities perform law enforcement duties with respect to activities occurring within their jurisdictional sea areas, over ships flying the same flag on the high seas, and over certain international crimes at sea.Footnote ¹¹ Third, warships and military aircraft customarily conduct hydrographic surveys and other data-gathering activities through seabed devices or other onboard structures to improve navigational safety and to obtain strategic information about the targeted area.Footnote ¹² Fourth, States routinely conduct intelligence collection activities or espionage, which may include the use of airborne and ship-based maritime surveillance systems and military devices, installations and structures on the seabed.Footnote ¹³

Any maritime State, large or small, may use its sea power to secure legitimate uses of ocean space to provide national security, in terms of both self-defence and the capacity to deploy military force overseas for warfare and peaceful purposes.Footnote ¹⁴ In fact, the use of military force to project power and influence over international relations has long been a traditional weapon in the diplomatic arena – the very term ‘gunboat diplomacy’ confirms the historic use of naval forces as a coercive element in achieving national goals.Footnote ¹⁵ Therefore, States possessing strong maritime forces have always favoured more liberal legal regimes for the ocean. The United States, for example, has ‘traditionally maintained a strong Navy to preserve the freedom of the seas and to support the global commitments associated with its forward defense strategy’ with the aim to ensure political persuasion, reassure allies, deter political adversaries and influence regional events.Footnote ¹⁶ These political imperatives have pushed maritime powers to seek the greatest freedom for military uses of the sea when developing the legal regimes of maritime zones.

The freedom to use ocean space for military purposes has never been without challenges and contradictions. The presence of a foreign navy in a nearby sea area is considered to pose a threat to the security and integrity of the coastal State and has provoked conflicts between the coastal State and the operating State.Footnote ¹⁷ Restrictions on military activities in coastal areas were commonly used in times of crisis and international confrontation. For example, during the Falkland/Malvinas conflict in 1982, the United Kingdom declared a 200 NM maritime exclusion zone around the islands and then replaced it by a total exclusion zone that banned the entry of all Argentine warships, naval auxiliaries and aircraft.Footnote ¹⁸

Within adjacent sea areas, the competition has always been between the coastal State’s intention to control all military activities for its exclusive use and the desire of other States to freely use the sea for their own or common interests.Footnote ¹⁹ Over time, the freedom to use the sea for military purposes has been affected by the elongation of the extent of the territorial sea and the creation of various functional jurisdiction zones.

6.1.2 Codification of the Law of Military Uses of the Sea

The development of international law in the twentieth century has witnessed the growth of an international consensus in support of increasing restrictions on the use of force in international relations.Footnote ²⁰ The broad prohibition on the threat or use of force in the Charter of the United Nations (UN Charter) represents an achievement of profound importance for the strengthening of international law.Footnote ²¹ This development, although it goes beyond the scope of the codification of the law of the sea, influenced the discussion of military uses of ocean space at the three United Nations Conferences on the Law of the Sea.Footnote ²²

The historical claims of a coastal State’s sovereign rights over the continental shelf was formalised in the 1958 Convention on the Continental Shelf, and refined in UNCLOS.Footnote ²³ The law of the sea acknowledges the sovereign rights of coastal States over the continental shelf, including the outer continental shelf that extends beyond 200 NM from the baselines, for the exploration and exploitation of the seabed and its natural resources, while preserving the freedom to lay submarine cables and pipelines for all States.Footnote ²⁴ The emplacement of military objects on or beneath the seabed floor and subsoil, one of the most important military uses of the sea, is not explicitly permitted or prohibited by these two conventions.Footnote ²⁵

When the 1958 Convention on the Continental Shelf was being negotiated, India proposed that the continental shelf should not be used by any State for the purpose of building military bases or installations, but this was rejected by thirty-one votes to eighteen.Footnote ²⁶ Although the final articles did not include an explicit permission, it was believed that, at least in 1958, the traditional high seas freedoms included the right to emplace military installations and devices on or in the seabed of the continental shelf.Footnote ²⁷ The additional coastal States’ sovereign rights over the continental shelf, as intrusions on the high sea freedoms, are limited to ‘the purpose of exploring it and exploiting its natural resources’ without affecting the legal status of the superjacent waters or airspace above those waters.Footnote ²⁸ The coastal State’s sovereign rights do not automatically apply to the military field, which remains to be governed by the high seas regime.Footnote ²⁹ There are, however, limitations on the freedom to use the continental shelf for military purposes. As a traditional high seas freedom, States wishing to emplace weapons, installations and other military devices on the continental shelf are obliged to do so with reasonable regard to the interests of other States in the exercise of their freedom of the high seas.Footnote ³⁰ Additionally, it can be argued that the use of the continental shelf for military purposes by a foreign State, similar to the laying or maintenance of submarine cables or pipelines, is subject to the coastal State’s right to ‘take reasonable measures for the exploration of the continental shelf and the exploitation of its natural resources’.Footnote ³¹

The freedom to use the seabed for military purposes is further restricted by the 1971 Seabed Treaty, which came into force in 1972 and has ninety-four State parties.Footnote ³² The 1971 Seabed Treaty recognises the common interest of humankind to promote the peaceful use of the seabed and the ocean floor, and contributes to the process of general and complete disarmament under strict and effective international control.Footnote ³³ All State parties are obligated

Nevertheless, the 1971 Seabed Treaty only concerns the prohibition on the use of nuclear weapons and other types of weapons of mass destruction, which were considered to have special verification procedures.Footnote ³⁵ The freedom to use other, less destructive weapons or military devices on the seabed and ocean floor was not affected by the 1971 Seabed Treaty so long as their use did not interfere with international navigation or other legitimate uses of the ocean.

During the negotiation of the 1971 Seabed Treaty in 1970, the United Nations General Assembly (UNGA) adopted the Declaration of Principles Governing the Seabed and the Ocean Floor (Declaration of Principles).Footnote ³⁶ The Declaration of Principles explicitly reserves the seabed and the ocean floor and subsoil thereof beyond the limits of national jurisdiction exclusively for peaceful purposes, ‘without prejudice to any measures which have been or may be agreed upon in the context of international negotiations undertaken in the field of disarmament and which have be applicable to a broader area’.Footnote ³⁷ Although UNCLOS does not contain any provisions on disarmament or arms control in ocean space, the thrust of discussion at the Third United Nations Conference on the Law of the Sea (Third Conference) and the final provisions are premised upon the guidelines established by the Declaration of Principles and the 1971 Seabed Treaty.Footnote ³⁸

Safeguarding free naval movement was one of the primary motivations of the major maritime powers in negotiating UNCLOS in light of the irreversible trend of extended coastal States’ claims.Footnote ³⁹ Meanwhile, contrasting proposals were made by Malta and other States at an early stage to include coastal States’ security rights and jurisdiction in the EEZ.Footnote ⁴⁰ Since it was not possible to reconcile this disagreement, military uses were left out from the formal debate and consequently not expressly addressed in UNCLOS.Footnote ⁴¹

With the establishment of the EEZ, there is an important difference between the legal regimes of the areas within and beyond the 200 NM limit. As its name indicates, the primary purpose of establishing the EEZ is to maximise the economic benefits of the coastal State in the adjacent sea area. Consequently, the rights over natural resources, including fishing, jurisdiction to construct artificial islands for all purposes and installations or structures for economic purposes, and to conduct marine scientific research in the EEZ, have been drastically curtailed compared to those on the high seas, and are subject to the jurisdiction of the coastal State.Footnote ⁴² However, the important high seas freedoms for communication have been explicitly preserved. All States enjoy the freedoms of ‘navigation and overflight and of the laying of submarine cables and pipelines, and other internationally lawful uses of the sea related to these freedoms’.Footnote ⁴³ There was no explicit reference to military activities in the current attribution of rights and freedoms in the EEZ, which veraciously fall under the realm of unattributed rights and duties based on the sui generis character of the EEZ.

On the one hand, the coastal State has sovereign rights and functional jurisdiction in the EEZ, as well as over the continental shelf. These are ‘sovereign rights’ exercised ‘for the purpose of exploring and exploiting, conserving and managing the natural resources’ and ‘jurisdiction’ in respect of certain other specified activities and purposes in conjunction with consequential duties.Footnote ⁴⁴ Military uses, however, are not automatically included in these sovereign rights and jurisdiction. This is consistent with the drafting history of the provisions concerning the coastal State’s sovereign rights over the continental shelf.Footnote ⁴⁵

On the other hand, States hold different views with regard to whether the freedom to conduct military activities in a foreign EEZ was automatically included in Article 58(1) during the negotiation of UNCLOS and after its adoption.Footnote ⁴⁶ The original version of Article 58, which preserves the freedoms for all States in the EEZ, appeared in the 1975 text produced by the Evensen Group, and read as ‘the freedoms of navigation and overflight and of the laying of submarine cables and pipelines and other internationally lawful uses of the sea related to navigation and communication’.Footnote ⁴⁷ The Castañeda-Vindenes Group replaced ‘navigation and communication’ with ‘these freedoms’ and added ‘such as those associated with the operation of ships, aircraft and submarine cables and pipelines, and compatible with the other provisions of [UNCLOS]’.Footnote ⁴⁸ Subsequent attempts to limit the scope of the proposed high seas freedoms in the EEZ were not accepted.Footnote ⁴⁹ The formula proposed by the Castañeda-Vindenes Group was adopted as part of the final text of Article 58(1). The change to ‘related to these freedoms’ considerably clarified and possibly expanded the freedoms preserved in the EEZ.Footnote ⁵⁰ It has been argued that international law historically considers military activity a lawful use of the high seas associated with the operation of warships and military aircraft exercising the freedoms of navigation and overflight.Footnote ⁵¹ Therefore, these changes served the intention of preserving the maritime State’s military uses rights in the EEZ and arguably included naval operations under ‘other internationally lawful uses of the sea’.Footnote ⁵²

However, a number of States made declarations when signing UNCLOS to express their opinion on these controversial aspects of military uses of the sea. Brazil declared that ‘the provisions of the Convention do not authorise other States to carry out in the exclusive economic zone military exercises or manoeuvres, in particular those that imply the use of weapons or explosives, without the consent of the coastal State’.Footnote ⁵³ Similar declarations and positions are maintained by Bangladesh, Cabo Verde, Ecuador, India, Malaysia, Pakistan, Thailand and Uruguay.Footnote ⁵⁴ In contrast, other maritime States have expressly rejected such limitations on the traditional freedom of navigation.For example, Germany specifically stated:

Italy, the Netherlands and the United Kingdom made similar statements.Footnote ⁵⁶

The question of military uses of the sea touches on political sensitivities and balance of power paradigms that were deliberately avoided during the negotiations at the three UN Conferences on the Law of the Sea. As a result, there is no provision in UNCLOS that clearly states whether the EEZ can be used for military purposes by either the coastal State or other States. The negotiation history and subsequent State practice fail to reveal a unified interpretation of relevant provisions in Part V. Regardless of the attribution of the right to use the EEZ for military purposes, there are certain rules to follow when conducting military activities therein. The general requirement is that the EEZ is reserved for peaceful purposes only, and all States must refrain from any threat or use of force inconsistent with general international law.Footnote ⁵⁷ In addition, States must have due regard to each other when exercising their legitimate rights and performing their duties.Footnote ⁵⁸

6.1.3 Obligations in Conducting Peacetime Military Activities

6.2.1 National Security Interests at Sea

Freedom of the seas, especially the free movement of military forces, has come to be regarded as essential for maintaining and advancing the national security interests of States.Footnote ¹¹⁴ However, national security interests alone are not a solid foundation for seeking to qualify the freedom to use the sea under the jurisdiction of another State for military purposes, as security interests are adjusted according to the changing international environment and are often confronted by the extension of national jurisdiction by the coastal State for security purposes.Footnote ¹¹⁵ The scope and meaning accorded to the notion of national security at sea – however different according to the coastal State or other States – influence which interests need to be protected and which activities need to be regulated.

States, coastal or landlocked, large or small, use ocean space for a great variety of purposes under many different circumstances.Footnote ¹¹⁶ The ocean is not only the place for natural resource development but also the centre of sea lanes communication and other human activities, including military activities.Footnote ¹¹⁷ Ensuring the use of the ocean for military training and planning, manoeuvres, weapons testing or other military operations is essential for maintaining and enhancing the capability of States to protect their security interests at sea.Footnote ¹¹⁸ Consequently, the adjacent sea areas are of crucial importance to promoting States’ strategic and military interests. For these purposes, States are advancing claims not only to the use of ocean space under their jurisdiction but also to securing effective and efficient access to the ocean space of others, as well as to sharing in the benefits of using the high seas.Footnote ¹¹⁹

On the one hand, coastal States have concerns in relation to national security interests and the protection of natural resources and the marine environment in the adjacent sea areas and tend to extend their control as far as possible to prevent threats coming from the sea.Footnote ¹²⁰ This includes placing limitations on foreign military activities in the EEZ.Footnote ¹²¹ The development of new military technologies has enabled the proliferation of a number of small and medium-sized navies to control their immediate maritime domains, which contributes to an overall trend in which more States are in favour of limiting the freedom of use of the seas.Footnote ¹²² China, for example, has on various occasions protested and challenged foreign military activities, especially reconnaissance conducted within its EEZ, and asserted that such activities endangered China’s national security interests.Footnote ¹²³

On the other hand, some States, notably powerful maritime States such as the United States, continue to consider maximising mobility in ocean space to be a fundamental national interest.Footnote ¹²⁴ These States argue that ensuring a naval power retains the authority for unimpeded access to the global commons will help to prevent the emergence of security threats on and above the ocean, especially in regions where coastal States have insufficient maritime capacity to maintain order without external assistance.Footnote ¹²⁵ This authority is known as ‘expeditionary sea power’, a military operation ‘to accomplish a specific objective on the periphery or in a foreign country’, which relies on the rapid deployment of naval forces.Footnote ¹²⁶ This concern reflects the situation in the Horn of Africa, where international authorities have been brought in to assist the coastal States, primarily Somalia, in gathering military forces for preventing and combatting piracy and international terrorists and for providing security and order at sea.Footnote ¹²⁷

A somewhat mixed set of policies towards security interests at sea shows that most States pursue policies that enhance their national security while simultaneously fighting to limit the strategic capabilities of their opponents. However, no State can, or should, simply assert control in its own maritime neighbourhood by restraining a foreign presence while seeking unlimited and unimpeded access to areas under the jurisdiction of another State. In addition, the race for control may lead to a situation where States are suspicious of each other’s intention in asserting power, and in return seek to accumulate increased power, but not necessarily feel more secure.Footnote ¹²⁸ Unless there is a self-sustaining process built on mutual understanding, this situation will become a vicious cycle that may provoke unnecessary conflicts, especially in times of political intensity.

It is inevitable that States want to pursue their national security interests at sea, but their approaches to achieving security vary significantly since they have different perspectives on what constitutes their prioritised interests at a given time. Although contributing to ‘the strengthening of peace, security, co-operation and friendly relations among all nations’ is a goal of the codification and progressive development of the law of the sea, security interests have never been clearly recognised in the EEZ under UNCLOS.Footnote ¹²⁹ However, the recognition of coastal States’ sovereign rights in the EEZ has given them a broader capacity to regulate activities taking place within adjacent sea areas and to prevent threats to their economic interests. It is often in this respect that some coastal States use creative interpretations of their granted rights to incorporate security interests in their EEZ.

6.2.2 Security Claims over the Exclusive Economic Zone

Within the territorial sea, foreign vessels must not act in a manner ‘prejudicial to the peace, good order or security of the coastal State’, but such language was not included in the provisions concerning either the contiguous zone or the EEZ.Footnote ¹³⁰ The desire to protect sovereignty and national interests has driven some States to become more creative and expansive in their definition and interpretation of national security interests, most frequently beyond the limit of their territorial seas.Footnote ¹³¹ State practice reveals three main approaches: claiming security interests in the contiguous zone; claiming jurisdiction over military surveys or the use of military structures or installations in the EEZ; and requiring consent for the conduct of military activities in the EEZ, especially military manoeuvres involving the use of weapons or explosives (Table 6.1).

It is notable that some States have retreated from their security claims in the EEZ in association with broader territorial sea claims. Chile, for example, was the first Latin American State to proclaim a 200 NM sovereign maritime zone in 1947, but brought its claims in line with UNCLOS in 1986.Footnote ¹³² Nicaragua, which once claimed sovereignty and jurisdiction over the adjacent sea to 200 NM that was only open to the innocent passage of foreign merchant vessels, has since adjusted its claims in accordance with UNCLOS.Footnote ¹³³ The same practice is observed by Liberia and Somalia, which rolled back from a claim of 200 NM territorial sea and established maritime zones according to UNCLOS.Footnote ¹³⁴

No fewer than thirty coastal States have explicitly sought to apply restrictions to the movement or operations of foreign warships, military aircraft or military devices in the EEZ for the purpose of safeguarding their security interests. These claims have been alleged as being inconsistent with UNCLOS and have been challenged and protested by other States, most notably the United States.Footnote ¹³⁵ In addition, eleven States made objecting declarations for those coastal States that prohibited foreign military activities in the EEZ without permission. These include Belgium, Finland, Germany, Ireland, Italy, Latvia, the Netherlands, Italy, Sweden, the United Kingdom and the United States, with some arguing that the coastal State’s rights and jurisdiction in the EEZ ‘do not include the rights to obtain notification of military exercises or manoeuvres or to authorize them’.Footnote ¹³⁶

6.2.3 Protection of Security Interests as a Residual Right in the Exclusive Economic Zone

It is clear that security interests exist in maritime areas and a number of States have claimed security interests in the EEZ without specifying the legal basis for their claims. As discussed earlier, there are different approaches to protecting a State’s security interests in the EEZ. While several coastal States have adopted the position that they have been granted jurisdiction over all military activities to prevent security threats in the EEZ, other States insist that the right to conduct military activities is included in the preserved high seas freedoms.Footnote ¹³⁷ As both sides argue for their right to claim or prohibit military activities in the EEZ, it is uncertain which side will prevail.Footnote ¹³⁸ At the debate on ‘peaceful uses of ocean space: zones of peace and security’ in 1976, Madagascar declared that it

Many developing States at the meeting echoed this position. However, this debate did not reach any conclusion on whether military activities should be permitted or prohibited in the EEZ. Nearly half-a-century later, the situation that Madagascar could not accept continues.

A possible solution to resolve these conflicting positions is to treat the protection of security interests, including the core element of asserting the right to conduct military activities, as a residual right in the EEZ given the lack of explicit reference in UNCLOS.Footnote ¹⁴⁰ The conflict is primarily between the need to conduct certain military activity to achieve the protection of the security interest of one State and the interests of another State. As such, whether a State has the right to conduct certain military activity in a given context is determined in such a way to ensure a balance between different States for protecting their respective interests.Footnote ¹⁴¹ Among the declarations and statements made by States upon ratification of and accession to UNCLOS, Belgium, Ecuador, Germany, Italy, the Netherlands, Sweden and Uruguay made explicit references to the residual rights in the EEZ that are linked with the right to conduct military activities.Footnote ¹⁴²

The guidance provided for resolving conflicts of residual rights in UNCLOS Article 59 is that it is to be ‘resolved on the basis of equity and in the light of all the relevant circumstances, taking into account the respective importance of the interests involved to the parties as well as to the international community as a whole’. Article 59 reaffirms the characteristic of the EEZ as a sui generis zone, which provides no presumption in favour of either party, but rather a basis for both sides to argue for rights and jurisdiction over military activities, as discussed in Chapter 3.Footnote ¹⁴³

Security interests at sea present an overlapping situation where different States can advance their claim over the same military activity for different purposes. The prospect of classifying the protection of security interests in the EEZ as a residual right means that such rights are not automatically assigned to either the coastal State or other States, and the conflict arising from their exercise should be resolved ‘on the basis of equity and in the light of all the relevant circumstances’ within a given context.Footnote ¹⁴⁴ When reviewing ‘all the relevant circumstances’, one must take into consideration the formula of attributing rights and freedoms between the coastal State and other States. As such, those favouring the coastal State must be adequately associated with their sovereign rights over natural resources and explicitly recognised jurisdiction whereas those favouring other States are closely associated with the recognised freedoms. Exercising the right to conduct military activities for security purposes, as with the exercise of other rights and freedoms, must be for peaceful purpose only and with due regard to other States’ co-existing rights and duties.

6.3.1 Navigation, Overflight and Military Manoeuvres

Every State, whether coastal or landlocked, has the right to sail ships and fly aircraft entitled to fly its flag in and above the EEZ.Footnote ¹⁴⁶ As customarily recognised, the freedom of navigation and overflight has never been absolute, in that it must be exercised for peaceful purposes only and with reasonable regard to the interests of other States in exercising their rights and freedoms, as well as fulfilling other conditions laid down in international law.Footnote ¹⁴⁷ Such freedoms are subject to further restrictions in the EEZ as they need to be compatible with the sui generis legal regime.Footnote ¹⁴⁸

The right of all States to navigate a military ship or fly a military aircraft in the EEZ must be exercised for peaceful purposes only. The desire to establish a legal order for the seas that will facilitate international communication and promote peaceful use of the seas is clearly recognised in the Preamble and repeated in various provisions of UNCLOS.Footnote ¹⁴⁹ As discussed earlier, the ‘peaceful purposes/uses’ obligation does not exclude the simple movement of any military ships or aircraft in the EEZ.Footnote ¹⁵⁰

In exercising the freedoms of navigation and overflight in the EEZ, States must give due regard to the rights and duties of other States using the same area. In terms of freedoms exercised by a foreign State, it must comply with the laws and regulations adopted by the coastal State in accordance with UNCLOS and other rules of international law.Footnote ¹⁵¹ However, military entities enjoy immunity from coastal State jurisdiction in the EEZ, especially laws and regulations on the protection and preservation of the marine environment.Footnote ¹⁵² This immunity is based on the grounds of State sovereignty and the principle of equity, because one State is not to be subjected to the jurisdiction of another.Footnote ¹⁵³ When a foreign military entity violates a coastal State’s rights and jurisdiction, the coastal State may require the vessel to leave the operational site immediately and the flag State assumes responsibility for any loss or damage resulting from its activities.Footnote ¹⁵⁴

There is emerging State practice challenging the freedom of navigation for military vessels powered by nuclear sources because of concerns about radioactive ocean contamination.Footnote ¹⁵⁵ For instance, a nuclear-powered submarine with a 35 megawatt reactor produces about 22.4 grams of mixed fission products daily during operation, which after 100 days of disintegrating at the rate of 14.7 kilocuries, releases the equivalent amount of short-lived isotopes as a 0.42 kiloton atomic bomb.Footnote ¹⁵⁶ Despite the relatively good safety record of nuclear-powered vessels, there are concerns over irreversible damage to the ocean environment that might be caused by a large amount of radioactive release resulting from either intentional or accidental damage or sinking of such vessels.Footnote ¹⁵⁷ Numerous States restrict or forbid the movement of nuclear warships in their territorial sea and some have extended these restrictions to the EEZ.Footnote ¹⁵⁸ However, the fact that nuclear-powered warships pose a potential environmental threat is not sufficient grounds to deprive them of the freedom of navigation in the EEZ. It remains the flag State’s right and obligation to implement the appropriate preventative measures for these vessels.

Traditionally, military exercises and manoeuvres are considered operational activities as part of the freedom of movement and communication on the high seas.Footnote ¹⁵⁹ However, it is unclear, since the establishment of the EEZ, whether these activities are considered an internationally lawful use of the sea related to the freedom of navigation that are compatible with the EEZ legal regime, or are prohibited as incompatible with the EEZ regime, or are unattributed rights.Footnote ¹⁶⁰ State practice also shows great divergence on this issue, particularly those manoeuvres involving weapons testing or live fire exercise.Footnote ¹⁶¹ As stated earlier, upon signing or ratifying UNCLOS, Bangladesh, Brazil, Cabo Verde, Ecuador, India, Malaysia, Pakistan, Thailand and Uruguay explicitly declared that military exercises and manoeuvres, particularly those involving the use of weapons, are not permitted in the EEZ without the consent of the coastal State. Meanwhile, opposing declarations were made by Belgium, Finland, Germany, Italy, Sweden, the Netherlands and the United Kingdom.

It is a matter of fact that States routinely conduct military exercises and manoeuvres at sea, including in their own EEZ and in foreign EEZs, as well as on the high seas, either individually or jointly with the participation of the coastal State and a third State.Footnote ¹⁶² These exercises, including missile testing and launching weapons and planes from an aircraft carriers or other warships, are important for military forces to test their strategic deployment and fighting skills in a broad range of scenarios, including evolving crisis and conflict situations.Footnote ¹⁶³ For example, the North Atlantic Treaty Organization (NATO) routinely conducts large-scale military training and exercises.Footnote ¹⁶⁴ NATO regularly deploys maritime forces in the Baltic Sea in order to exhibit forward presence, maintain a credible and capable defensive capability, and contribute to operational coherence among allied naval forces to support greater regional security and stability.Footnote ¹⁶⁵

The coastal State, when conducting military exercises and manoeuvres within its EEZ, must have due regard to the rights and duties of other States and must maintain peaceful purposes. UNCLOS is silent on whether the coastal State may close a certain sea area to navigation for such activities, in contrast to the explicit reference to the right to suspend innocent passage temporarily ‘for the protection of its security, including weapons exercise’.Footnote ¹⁶⁶ It may be argued that the coastal State could close a specified area within its EEZ for military exercises and manoeuvres provided that such closure has been duly published and is not impeding normal passage routes used for international navigation and overflight. NATO allies, for example, have used the Baltic Sea and the region surrounding it as a maritime training ground for over five decades. Known as the Baltic Operations (BALTOPS), the annual military exercise is aimed at delivering high-end training across the entire spectrum of naval warfare.Footnote ¹⁶⁷

Military exercises and manoeuvres conducted in the EEZ by a foreign State are likely to be challenged by the coastal State, particularly if such activities involve the use of weapons, and/or take place in disputed areas, and/or during periods of political tension. Numerous examples exist. The military exercises jointly conducted by the United States and South Korea were often denounced by the Democratic People’s Republic of Korea as ‘an irresponsible and dangerous action’ and a ‘rehearsal for war’, which they responded to with threats of nuclear war.Footnote ¹⁶⁸ China has firmly protested the annual joint military exercise between the Philippines and the United States, known as ‘Balikatan’ (shoulder-to-shoulder), and asserts that such activities have raised the risk of armed confrontation over the disputed South China Sea.Footnote ¹⁶⁹ Such protests concerning foreign military activities are also common in the Baltic Sea, the Black Sea and the Mediterranean Sea, particularly in relation to the tension between NATO and Russia. Both Latvia and Sweden protested Russia’s missile tests and military drills in the Baltic Sea in 2018 and 2020, respectively.Footnote ¹⁷⁰ With an acceleration of tension between Türkiye and Greece over their long-standing dispute concerning maritime rights and natural resources in 2020, both sides brought in allies to conduct military exercises and drills with the intention to demonstrate strength, and issued protests over the other side’s activities.Footnote ¹⁷¹ Despite these ongoing challenges by the coastal States, the ICJ concluded in Nicaragua (Merits) that the conduct of military manoeuvres closer to a coastal State’s border is not in breach of ‘the principle of forbidding recourse to the threat or use of force’.Footnote ¹⁷²

The operating State, either the coastal State or a foreign State, is obligated to adopt appropriate measures to ensure that its military entities act in a manner consistent with the environmental protection and preservation provisions in UNCLOS.Footnote ¹⁷³ Such measures must not impair operations or operational capabilities of such entities and must be reasonable and practicable.Footnote ¹⁷⁴ Such measures may include the assessment of environmental impacts and subsequent communication with potentially affected States.Footnote ¹⁷⁵ However, the vague language and general obligation leaves a coastal State little to no means to challenge foreign military activity based on environmental obligations. Likewise, it would be difficult for any foreign State to challenge a coastal State’s military activity conducted in its own EEZ on the basis of environmental obligation.

In summary, warships and military aircraft of all States enjoy the freedom of navigation and overflight in the EEZ, including the freedom to conduct military manoeuvres despite the lack of consensus in relation to their legalities among States.Footnote ¹⁷⁶ As long as these activities are conducted consistent with the due regard obligation and peaceful purposes, they are not prohibited in principle.Footnote ¹⁷⁷ Up until a certain point, foreign military presence and exercises are to be tolerated in the EEZ of a coastal State. In the problematic situation where weapons are used, there are a range of factors that would be applicable in determining whether their use fulfils these requirements, particularly the due regard obligation. These would include whether such use causes undue restriction on the freedoms of navigation and overflight, or causes harm to natural resources. The operating State must ensure that it fulfils these obligations and assumes responsibility if such exercises damage the rights and jurisdiction of the coastal State, or the freedoms of other States. In order to reduce tension, it would be a good practice for the operating State to give notice to the coastal State or other interested States and provide information of what, when and where such military exercises will take place. Moreover, given the circumstances and by the nature of the rights that could be affected by the military exercise, the operating State should initiate a certain level of consultation with the rights-holding State to fulfil their due regard obligation.Footnote ¹⁷⁸

6.3.2 Espionage, Intelligence Gathering and Surveillance

States have advanced the need to acquire knowledge of maritime areas, mainly through intelligence gathering activities, to make decisions about their national defence strategies.Footnote ¹⁷⁹ There is no general rule in international law that prohibits or limits activities of intelligence gathering beyond the limit of the territorial sea.Footnote ¹⁸⁰ Despite different interpretations on the legality of military intelligence gathering in the EEZ, in practice, States have tolerated such activities for a long time.Footnote ¹⁸¹ Peacetime military intelligence gathering, also known as reconnaissance or espionage, is principally conducted by space-based, airborne, ship-based and seabed-attached maritime surveillance systems, including cyber infrastructure.Footnote ¹⁸² Although peacetime military intelligence gathering does not per se violate international law, the method by which it is carried out might do so.

Satellite-based reconnaissance was initiated by the United States in 1958 to spy on the Union of Soviet Socialist Republics (USSR) and its allies.Footnote ¹⁸³ The Galactic Radiation and Background satellite system, the first satellite system for signal surveillance, detected radar as it passed within the line of sight of a transmitting radar system; it then beamed down the radar signals it intercepted to a network of ground stations and transferred them to magnetic tape, which was then taken by courier to the United States for analysis.Footnote ¹⁸⁴ The technology of the Galactic Radiation and Background satellite system is now obsolete, but conducting electronic surveillance from orbit continues to be a primary technique.Footnote ¹⁸⁵ Except in cases that use artificial islands, installations and structures for on-land stationing, conducting satellite-based reconnaissance in another State’s EEZ is less likely to interfere with the coastal State’s sovereign rights or jurisdiction.

Airborne surveillance systems are operated by military aircraft that collect both signal and electronic intelligence, which has the advantage of providing regular, real-time surveillance of the electromagnetic emissions in important parts of the spectrum that are undetectable from ground sites.Footnote ¹⁸⁶ Traditional manned aircraft can intercept and record the emissions of radar and other radio/electronic systems, as well as signals of computer-to-computer data traffic, and even phone traffic, to map air defence networks, airfields and missile batteries for target planning purposes.Footnote ¹⁸⁷ The advanced airborne facility involves unmanned aerial vehicles, which can be launched outside the EEZ on a pre-programmed mission without the launching ship or aircraft actually entering the zone itself.Footnote ¹⁸⁸ Since the coastal State’s jurisdiction in the airspace above the EEZ is limited to activities for the economic exploitation and exploration of the zone, such as the production of energy from wind, it would be difficult to challenge foreign airborne surveillance unless it interferes with these economic activities.Footnote ¹⁸⁹

Likewise, military surveillance ships are widely used to collect intelligence at sea. For example, the United States maintains six ocean surveillance ships as part of the twenty-one ships under the Military Sealift Command’s Special Mission programme,Footnote ¹⁹⁰ which routinely collects intelligence on the high seas and in foreign EEZs, despite diplomatic protests from China, India, Brazil and other States.Footnote ¹⁹¹ The surveillance ships conduct a variety of missions, including collecting signal and electronic intelligence; monitoring naval exercises, communications, or combatant surveillance; monitoring the movement of ballistic missile–carrying submarines; and using passive and active low-frequency sonar arrays to detect and track undersea threats.Footnote ¹⁹² Some of the detection techniques used by the surveillance ships – high-powered sonar arrays, for example – may disorient or injure whales and other marine mammals,Footnote ¹⁹³ which arguably could interfere with the coastal State’s sovereign rights to explore, conserve and manage such resources.

There have been increasing concerns regarding the legitimacy of certain highly advanced technologies used in intelligence gathering and surveillance. Particularly relevant in this context are active signals intelligence activities, some of which are deliberately provocative and are intended to generate responses from the targeted coastal State, while others may involve intercepting naval radar and emitters to locate, identify and track surface ships in the targeted areas.Footnote ¹⁹⁴ These activities do not have a direct impact on natural resources and appear to cause far greater interference with communication and defence systems of the targeted State. These highly provocative activities may cause or exacerbate conflicts, since many coastal States consider them hostile and incompatible with the peaceful purposes obligation.Footnote ¹⁹⁵

The lack of legal clarity in relation to espionage, intelligence gathering and surveillance in the EEZ has been problematic, especially in situations where such activities are conducted in a foreign EEZ.Footnote ¹⁹⁶ Alongside the firm position held by the United States, the United Kingdom also considers the airspace above the EEZ as international airspace, in which military aircraft of another State may lawfully fly ‘for the purpose of surveillance and observation of activities within that other state’s national airspace or territory’.Footnote ¹⁹⁷ China, on the other hand, constantly challenges unauthorised foreign intelligence-gathering and surveillance activities in its EEZ.Footnote ¹⁹⁸ China recognises that all States enjoy ‘the freedom of navigation and overflight and of laying submarine cables and pipelines, and shall enjoy other legal and practical marine benefits associated with these freedoms’ within the Chinese EEZ.Footnote ¹⁹⁹ However, the phrase ‘other legal and practical marine benefits associated with these freedoms’ is different from the expression of ‘other internationally lawful uses of the sea related to these freedoms’ used in UNCLOS Article 58(1). The phrase in the Chinese law only equals the expression of ‘such as those associated with the operation of ships, aircraft and submarine cables and pipelines’ that was used to exemplify ‘other internationally lawful uses’.Footnote ²⁰⁰ This language would narrow the scope of the associated freedoms enjoyed by other States, which is arguably intended to restrict foreign military activities in China’s EEZ.

The debate over foreign intelligence-gathering activities was highlighted in April 2001 when a US Navy EP-3 surveillance plane collided with a Chinese F-8 fighter jet approximately 70 NM southeast of Hainan Island, killing the Chinese pilot and making a forced landing at Lingshui Military Airport.Footnote ²⁰¹ The Chinese view was that the intelligence collected could be used for hostile purposes and such activity went far beyond the scope of overflight and abused such a freedom, breaching the due regard obligation and peaceful purposes, which constituted an infringement upon China’s sovereignty.Footnote ²⁰² The United States claimed it was engaging in a traditional military activity over international waters, which was legally permissible and conducted with due regard of China’s rights as a coastal State.Footnote ²⁰³ It is generally recognised that the airspace above the EEZ is governed by the ‘specific legal regime’ as established in UNCLOS, which is different from the international space asserted by the United States.Footnote ²⁰⁴ Thus, the United States military plane flying above the Chinese EEZ must fulfil the obligation of operating for peaceful purposes and have due regard to the rights and duties of China.Footnote ²⁰⁵ However, the mere assertion that performing reconnaissance in the EEZ constitutes an abuse of the right of overflight seems too weak to support China’s position of prohibiting the entrance of US aircraft altogether. The Chinese position is further weakened by its own increased surveillance activities in the East and South China Sea, particularly around disputed islands with Japan, as well as observing a US missile defence test off Alaska in 2017 and 2021.Footnote ²⁰⁶

There have been many incidents involving coastal States and foreign surveillance ships in Asian waters. In December 2001, the Japanese Coast Guard chased an alleged North Korean spy ship out of its EEZ using at least twenty-five vessels and fourteen aircraft, attacking and eventually sinking the suspected ship in China’s EEZ, killing the fifteen crewmembers on board.Footnote ²⁰⁷ The United States and China continue to have confrontations in the Yellow Sea, the East China Sea and the South China Sea, with China challenging the activities of US surveillance ships. Most notably, on 8 March 2009, five Chinese vessels surrounded the USNS Impeccable approximately seventy-five miles south of Hainan Island in the South China Sea and forced it to stop operating and leave the area.Footnote ²⁰⁸ The United States made a formal complaint, labelling the Chinese actions as reckless, unprofessional and unlawful; China responded that Impeccable had illegally engaged in intelligence data gathering and was in violation of Chinese domestic law and international law.Footnote ²⁰⁹ Given the ongoing tension around disputed islands in the East and South China Seas and the battle for maritime dominance between China and the United States in the Asia-Pacific region, the suspicion over foreign military surveillance activities will continue to provoke conflicts among the coastal State and operating States.Footnote ²¹⁰

The need to obtain intelligence in the EEZ seems even more important for the coastal State based on its security concerns. Coastal States are also not prohibited from conducting espionage, intelligence-gathering and surveillance activities in their EEZs provided that they are not impeding the freedoms of navigation and overflight and such activities are for peaceful purposes. In addition to the often secret espionage activities, coastal States are increasingly using air defence identification zones (ADIZ) and maritime identification zones to obtain information that could further complicate the debate on military intelligence gathering and surveillance activities in the EEZ.Footnote ²¹¹ These coastal surveillance regulations should have limited impacts on foreign military aircraft and ships, since they should be exempted given their immunity status. However, there has been some questionable State practice on the applicable regulations that were adopted with an aim to limit foreign espionage activities. China, for example, requires all aircraft entering the East China Sea ADIZ to submit flight plans and maintain communications through radio and radar, and will assert necessary armed response to non-compliant aircraft.Footnote ²¹²

Unlike in the territorial sea, where ‘any act aimed at collecting information to the prejudice of defence or security of the coastal States’ is forbidden, such activities are not specifically outlawed in the EEZ.Footnote ²¹³ Despite the ongoing debates, both the coastal State and other States have been conducting espionage, intelligence-gathering and surveillance activities in the EEZ. In general, these activities have the essential feature that the data generated are used for military purposes only and are not released to the public. It is often accepted that the operating State has the right to determine if a certain activity is of military nature and for military purposes, with other States having less means to question this categorisation.Footnote ²¹⁴ The coastal State, for instance, would have to accept that the data allegedly collected for military purposes does not have direct economic value and would not impede the normal exercise of its sovereign rights and jurisdiction. Nevertheless, the increasing sophistication of surveillance capabilities has put the appropriate balance between the coastal State and the operating State to a test, as the security interests recognised and protected in the territorial sea or even the territory of the coastal State may be infringed upon without the offender physically entering these areas.Footnote ²¹⁵ However, until the right to protect security interests is recognised in the EEZ, the coastal State does not have a strong legal position to challenge the legality of intelligence gathering and surveillance by a foreign State, other than the vague mutual due regard obligation and the prohibition on the threat or use of force.

6.3.3 Military Survey and Research

The military survey is another type of military activity that has been routinely conducted in the EEZ irrespective of the controversy over its legitimacy.Footnote ²¹⁶ It is closely related to the hydrographic survey, oceanographic survey and marine scientific research activities. UNCLOS has relatively clear rules on jurisdiction over marine scientific research in the EEZ, but since it does not provide definitions for any of these activities, States employ differing interpretations that may confuse the attribution of jurisdiction over a specific activity. Thus, there is often disagreement over whether surveys are a marine scientific research activity, and whether military surveys and research should be exempted from coastal State jurisdiction.

Marine scientific research, in general, refers to ‘any study or related experimental work designed to increase man’s knowledge of the marine environment’ that falls under coastal State jurisdiction in the EEZ.Footnote ²¹⁷ Hydrographic survey is defined by the International Hydrographic Organization as

Oceanographic survey is defined as ‘[a] study or examination of any physical, chemical, biological, geological or geophysical condition in the OCEAN, or any part of it. An expedition to gather DATA, samples or information to conduct such studies or examination’ (emphasis in the original).Footnote ²¹⁹

The 1958 Convention on the Continental Shelf distinguished between ‘purely scientific research into the physical or biological characteristics of the continental shelf’ and other resource-oriented research.Footnote ²²⁰ The former refers to activities that are solely intended to increase human knowledge about the ocean with the results made internationally available, regardless of their subsequent application, while the latter refers to those undertaken primarily for specific practical purposes, commonly known as applied scientific research.Footnote ²²¹ The coastal State may not normally withhold its consent for pure scientific research, but may reserve authorisation over applied scientific research.Footnote ²²²

UNCLOS does not distinguish survey from scientific research, but various articles refer to research and survey activities separately, and Part XIII deals solely with marine scientific research.Footnote ²²³ A close reading of the provisions shows that the separation only occurs in the context of special passage regimes, including innocent passage, transit passage and archipelagic sea lanes passage, to ensure such passage is ‘continuous and expeditious’.Footnote ²²⁴ It is unclear why survey activities have been singled out in these provisions, but State practice remains divided on whether UNCLOS established a separate legal regime for surveying.Footnote ²²⁵

UNCLOS nevertheless implies its acceptance of the different treatment between pure and applied scientific research as adopted in the 1958 Convention on the Continental Shelf. It requires that coastal States should normally ‘grant their consent for marine scientific research projects’ in their EEZs or on their continental shelves to be carried out ‘in order to increase scientific knowledge of the marine environment for the benefit of all mankind’, emphasising the right to reserve consent for projects for any specific practical purposes.Footnote ²²⁶ Surveys, both hydrographic and oceanographic, serve the purpose of obtaining knowledge of the condition of the waters and the seabed. Some survey activities also employ the same methods and equipment as scientific research, in particular oceanographic sampling, mid-water and ocean floor parameters, launch and recovery of hydrographic survey launches or other scientific packages, including the handling, monitoring and servicing of remotely operated vehicles.Footnote ²²⁷ Hence, surveys in general should be considered part of the broader scope of marine scientific research as a type of applied scientific research. However, certain specific survey activities may be exempted from coastal State jurisdiction if they can be assimilated to other preserved freedoms, such as cable surveys, which are regarded as activities associated with the operation of submarine cables.Footnote ²²⁸ Jurisdiction over hydrographic and oceanographic surveys is more controversial because they provide vital information to determine the geographical features of the seabed that facilitates the exploration and exploitation of natural resources, which are of great concern for coastal States’ economic interests.Footnote ²²⁹

The US Navy has adopted the definition of military survey as

Most of these activities can be classified under the category of hydrographic survey, subordinate to a broader definition of marine scientific research.Footnote ²³¹ The key element that the US Navy uses to differentiate military surveys from marine scientific research is the ‘military purposes’ whereby data is not made available to the public.Footnote ²³² The information generated during a military survey is essential for ‘effective submarine operations, anti-submarine warfare, mine warfare and mine countermeasures’, particularly in waters where ‘oceanographic and underwater acoustic conditions vary widely with uneven bottom topography, fast tidal streams and a relatively high level of marine life’.Footnote ²³³ Similar to the data collected by intelligence gathering and surveillance activities, a military survey provides the operating State important knowledge to make decisions about their defence strategies.

The United States routinely conducts military surveys and research seaward of foreign territorial seas and has continued to do so since the establishment of the EEZ.Footnote ²³⁴ It has also clearly stated that hydrographic surveys and military surveys are not marine scientific research.Footnote ²³⁵ The US Navy has eight ships dedicated to surveying and research. Two are general-purpose oceanographic research vessels that are manned by contracted commercial crews.Footnote ²³⁶ It also maintains six oceanographic survey ships as part of the twenty-one ships under the Military Sealift Command’s Special Mission programme.Footnote ²³⁷ These survey ships perform acoustic, biological, physical and geophysical surveys using multi-beam, wide-angle, precision sonar systems that are the same as used for hydrographic surveys to collect data on the ocean environment.Footnote ²³⁸ However, the United States insists that these naval operations are required not to be combined with marine scientific research activities.Footnote ²³⁹

In contrast, both China and India take the position that military hydrographic surveys fall under the scope of marine scientific research that is subject to the coastal State’s jurisdiction in the EEZ.Footnote ²⁴⁰ China requires foreign organisations or individuals that wish to conduct such activities in its EEZ to obtain approval from the competent authorities and observe the provisions of relevant Chinese laws, administrative rules and regulations.Footnote ²⁴¹ This requirement would forbid any foreign entity from conducting military surveys without explicit consent from the Chinese government. China has frequently confronted US military survey and research ships in its EEZ. For example, in September 2009, USNS Bowditch was confronted and followed by Chinese patrol planes and vessels in the Yellow Sea while doing oceanographic surveys, which led to a collision between a Chinese fishing vessel and Bowditch that damaged its sonar system.Footnote ²⁴² India also has restricted foreign military activities in its EEZ.Footnote ²⁴³ It challenged the USNS Bowditch for conducting military surveys in its EEZ in 2004, with India claiming that ‘the warship gathered data that could reveal much military information on the ocean environment, including identifying possible underground nuclear facilities and submarines. Such data helps reorient technology in undersea warfare and enemy ship detection’.Footnote ²⁴⁴

There is no general consensus in relation to military surveys and research in the EEZ.Footnote ²⁴⁵ It could be argued that surveys are a type of marine scientific research that should be regulated by the coastal State in the EEZ except those that can be exempted. The crucial issue is whether military surveys and research should be exempted from coastal State jurisdiction due to their military purpose. The data collected could be used to support the safety of navigation, increase the knowledge of the marine environment for economic purposes, or assist with warfare planning. In practice, the coastal State cannot be certain of the type and purpose of the survey or research that military entities are conducting in its EEZ, which tends to raise suspicions and provoke conflicts.Footnote ²⁴⁶ The coastal State may only challenge such activities if they violate its sovereign rights over natural resources or jurisdiction over marine scientific research, but they lack a legal basis to challenge such vessels for constituting a threat to its security interests.

Due to the highly political nature and sensitivity of the data collected, it seems unlikely that disputes on this matter will be easily resolved between States or settled by international courts and tribunals in the near future.Footnote ²⁴⁷ It would help to ease tensions if the operating State obeyed the due regard obligation and refrained from collecting data vital to the coastal State’s economic interests and gave assurances through notification of the survey time and location. The operating State may also release the data collected, wholly or partially, after a period of time when the secrecy is no longer needed. In particular, if the military research can ‘increase scientific knowledge of the marine environment for the benefit of all mankind’, the research data should be made available to the public.Footnote ²⁴⁸

6.3.4 Military Installations, Structures and Other Devices

Many maritime powers have deployed various military devices, installations and structures in and onto the ocean floor, including the seabed of foreign EEZs, that play a significant role in military uses of the sea.Footnote ²⁴⁹ These objects can be placed on the seabed directly, or through storage and other facilities, including submarines, submarine cables, platforms or installations fixed onto the seabed.Footnote ²⁵⁰ Examples of these objects include undersea data centres, espionage equipment, sonar monitoring and surveillance systems, navigation aids for submarines and warships, armed mines and other weapon systems.Footnote ²⁵¹ Given the lack of explicit attribution of the right to deploy military objects in the EEZ, the attribution and exercise of such a right should follow the rules established in Article 59 of UNCLOS and the obligations of exercising co-existing rights. Each type of military object will be discussed below to determine whether they are more closely associated with the communication freedoms under Article 58, or with the sovereign rights and jurisdiction of the coastal State, particularly its jurisdiction over ‘installations and structures’ under Article 60.

Submarines and other warships deploy listening equipment and other detection and communication devices to monitor the positions, movement and numbers of submarines or other military forces in the targeted area.Footnote ²⁵² They are essential components of anti-submarine warfare, which dates back to the First World War when ‘the British effectively used listening devices (hydrophones) and aircraft to detect German U-boats, and depth charges and mines to sink them’.Footnote ²⁵³ The continental slope is an ideal area to place anti-submarine warfare sonar devices, as they can pick up sounds at a greater distance over the deep seabed, and the advancement of technology over the past five decades provides a high degree of accuracy.Footnote ²⁵⁴ These data provide important information to assist with targeting and navigation, as well as scouting another State’s military capability and movements, which could be essential in avoiding surprise attacks.Footnote ²⁵⁵ It seems that these monitoring and surveillance devices are more closely associated with the operation of ships than the exploration and exploitation of natural resources. States often argue that the use of such devices is essential to protect their security interests, but many of them still challenge the deployment of these devices by a foreign State within their EEZ or on their continental shelf.

States are also deploying various expendable marine instruments to collect data about the water column for a variety of purposes, including modelling global warming and other hydrologic changes, locating natural resources and monitoring the movement of submarines and other naval operations.Footnote ²⁵⁶ Both warships and scientific research ships routinely deploy expendable instruments into the ocean, with an estimated deployment of millions of such instruments worldwide between the 1960s and 1990s.Footnote ²⁵⁷ Underwater explosions or disposal of unwanted explosives at sea can have harmful effects on marine living creatures and the environment due to the shock waves and release of toxic chemicals.Footnote ²⁵⁸ When such expendable instruments are used as part of a marine scientific research project in the EEZ, they must be authorised by the coastal State.Footnote ²⁵⁹ Given that their use is mainly for navigation and survey purposes, military forces of all States may deploy such instruments in the EEZ. Their use must observe the obligations set out in UNCLOS for military activities at sea. In particular, the use of expendable instruments in the EEZ must not interfere with the exercise of another States’ rights and duties, including the coastal State’s sovereign rights and jurisdiction.Footnote ²⁶⁰ The operating State should also adopt appropriate measures to ensure that their normal uses are consistent, as far as is reasonable and practicable, with environmental protection and preservation requirements.Footnote ²⁶¹

States have traditionally deployed armed mines and other weapon systems on the seabed. The 1971 Seabed Treaty prohibits the emplacement of nuclear weapons and other weapons of mass destruction and of installations specially designed to store, test or use them on the seabed beyond 12 miles from shore.Footnote ²⁶² But the treaty is silent on other conventional weapons. It could be argued that, in peacetime, the emplacement of weapons on the continental shelf by both the coastal State and other States is not in full compliance with the peaceful purposes obligation except for legitimate self-defence as recognised by the UN Charter.Footnote ²⁶³ In addition, deploying weapon systems by a foreign State in a nearby marine area poses direct threats to a coastal State’s security interests, along with the possibility of causing irreparable damage to the marine environment, and interferes with the exercise of the rights and freedoms by other States in the EEZ.Footnote ²⁶⁴

Submarine cables, including the repeaters, could also be used for military purposes.Footnote ²⁶⁵ The military may build, purchase or lease a submarine fibre optic cable for a variety of purposes, including telecommunications, acoustic monitoring and bilateral communications.Footnote ²⁶⁶ The US Navy, for example, maintains two cable laying/repair ships to transport, deploy, retrieve and repair undersea cables.Footnote ²⁶⁷ Moreover, the military could use a purpose-built submarine or unmanned underwater vehicle to physically tap communication cables in order to collect, alter or jam any traffic transmitted through them, particularly in relation to cyber operations.Footnote ²⁶⁸ Furthermore, as technology develops, the military could build undersea data centres associated with or without a submarine cable.Footnote ²⁶⁹ The freedom to lay submarine cables, including uses associated with the operation of cables, should apply to military cables.Footnote ²⁷⁰ Tapping operations of submarine cables in the EEZ do not constitute a violation of the rights of the coastal State unless they interfere with the exploration and exploitation of the seabed and its natural resources.Footnote ²⁷¹ The establishment of military undersea data centres, either an installation or structure, by a foreign State in the EEZ would be questionable if it interferes with exercise of the rights of the coastal State.Footnote ²⁷²

It is relevant to clarify the scope of a coastal State’s jurisdiction under Article 60 over the use of installations and structures in the EEZ.Footnote ²⁷³ The coastal State’s ‘exclusive right to construct and to authorize and regulate the construction, operation and use of’ installations and structures is limited to those ‘for the purposes provided for in Article 56 and other economic purposes’ and those that ‘may interfere with the exercise of the rights of the coastal State in the zone’.Footnote ²⁷⁴ Apart from resource-related activities, these economic purposes include ‘other activities for the economic exploration and exploitation of the zone, such as the production of energy from the water, currents and winds’, marine scientific research, and the protection and preservation of the marine environment.Footnote ²⁷⁵ A plain reading of this provision may lead to the conclusion that the use of military objects on the seabed, which generally are not for resource-related purposes, is exempted from the exclusive right of the coastal State. However, a coastal State may find legitimate grounds to challenge the use of foreign military installations or structures if they interfere with the exercise of its rights and jurisdiction in the EEZ. The extension to potential interference expands and strengthens the legal basis for the coastal State to challenge the deployment of these military objects.Footnote ²⁷⁶

Under the 1958 Convention on the Continental Shelf, the coastal State is entitled to construct and maintain or operate on the continental shelf ‘installations and other devices’ necessary for the exploration and exploitation of its natural resources.Footnote ²⁷⁷ Under UNCLOS, the language was changed to ‘installations and structures’ and the term ‘devices’ is used separately elsewhere.Footnote ²⁷⁸ This distinction indicates that the two terms have a different connotation. The term ‘devices’Footnote ²⁷⁹ refers to objects that operate in certain mechanical or chemical ways or have attributes permitting their use for the performance of certain tasks, while the term ‘structures’Footnote ²⁸⁰ refers only to those lacking operative characteristics or functional attributes.Footnote ²⁸¹ The term ‘structures’ is a narrower concept than ‘devices’.Footnote ²⁸² This interpretation is confirmed in Article 209, where the two terms are phrased as ‘vessels, installations, structures and other devices’, indicating that the term ‘devices’ includes ‘structures’.Footnote ²⁸³ Consequently, ‘devices’ that cannot be considered as ‘structures’ are not objects that fall under the exclusive rights and jurisdiction of the coastal State.Footnote ²⁸⁴

Under contemporary international law, it is arguable that any State can use the ocean floor of the EEZ and the continental shelf to deploy and service military devices, installations and structures that do not fall under the jurisdiction of the coastal State, even with the contrary argument from a coastal State that is often backed by political objections.Footnote ²⁸⁵ Nevertheless, the uses of these military objects must fulfil important obligations. First, such uses of the seabed must be for peaceful purposes only, and weapons systems should not be deployed unless for legitimate self-defence purposes. Second, the operating State must comply with the due regard obligation, whereby there should not be any unreasonable interruption to the exercise of rights and freedoms of other States, particularly those of the coastal State. However, there is a considerable difference between the operating State fulfilling its obligations and the coastal State forbidding these activities, as the latter denies such uses as a freedom.

6.3.5 Remarks on Conflicting Practices

The preceding discussion demonstrates that, even though there is no clear attribution of jurisdiction over military activities in the EEZ, both coastal States and other States routinely conduct such activities. The key controversies are that States have different interpretations of whether a foreign State may conduct certain military activities in the EEZ of another State, and what kind of restrictions are placed on the operating State.

The resolution of conflicts regarding the conduct of military activities in the EEZ should follow the formula provided by Article 59. Certain foreign military activities would be restricted to give priority to the coastal State’s economic interests in the EEZ.Footnote ²⁸⁶ For example, foreign military activities must not involve the exploration and exploitation of natural resources in the EEZ, nor can they unduly interfere with the exercise of the EEZ-related rights of the coastal State.Footnote ²⁸⁷ Military manoeuvres, especially those that involve the use of weapons, should be balanced with the coastal State’s sovereign rights either through notification or consultation. However, military activities that do not interfere with the coastal State’s sovereign rights can be carried out by all States. These activities include military navigation and overflight, espionage, intelligence gathering, surveillance, military survey and the use of military devices.

The exercise of the right to conduct all peacetime military activities, by both the coastal State and other States, must fulfil the reciprocal due regard obligation to other States. Military activities that have a severe impact on natural resources or cause irreparable damage to the marine environment could be considered as violating the coastal State’s rights and jurisdiction.Footnote ²⁸⁸ For example, if foreign military manoeuvres and ballistic exercises take place in a fishing area, or in close proximity to an active offshore oil platform, or as near as 13 NM from the coast, the coastal State may oppose or impose certain requirements.Footnote ²⁸⁹ In turn, the coastal State should not conduct any military activities that unduly impair the freedoms of navigation and overflight, the laying of submarine cables and pipelines, and other internationally lawful uses of the sea related to these freedoms.

In cases where the coastal State determines that the foreign warship or military aircraft has abused its rights in the EEZ, the coastal State, even though it cannot exercise enforcement jurisdiction, may require the departure of foreign military entities from this maritime area.Footnote ²⁹⁰ In addition, if the alleged wrongful act has caused any loss or damage to the coastal State, the flag State must bear international responsibility for such wrongdoings.Footnote ²⁹¹ In cases where the foreign State asserts that its freedoms have been affected by the coastal State’s conduct of a military activity, it may challenge such conduct initially through diplomatic channels. States must be cautious as to what measures are used against another State’s warship or military aircraft. As a warship is ‘an expression of the sovereignty of the State whose flag it flies’, ‘any action affecting the immunity of warships is capable of causing serious harm to the dignity and sovereignty of a State’ and hence ‘imping[e] on the maintenance of international peace and security’.Footnote ²⁹²

It is noteworthy that disputes concerning military activities are optional exceptions to the compulsory third-party dispute settlement procedures established by UNCLOS. Upon signing, ratifying or acceding to UNCLOS, or at any time thereafter, any State may declare in writing that it does not accept the compulsory procedures with respect to ‘disputes concerning military activities, including military activities by government vessels and aircraft engaged in non-commercial service’.Footnote ²⁹³ As of 2024, twenty-four States have made declarations to exclude themselves from the compulsory procedures with regard to this exception.Footnote ²⁹⁴ Moreover, the United States holds the opinion that, under Article 298(1)(b), each State party has the exclusive right to determine whether its activities are or were ‘military activities’ and that such determinations are not subject to review.Footnote ²⁹⁵ The distinction between certain military activities and non-military activities, particularly survey, research and law enforcement activities has blurred considerably. The distinctive feature of a military activity is based ‘primarily on an objective evaluation of the nature of the activities in question, taking into account the relevant circumstances in each case’.Footnote ²⁹⁶ Given the political nature of disputes concerning military activities, it is not very likely that this kind of dispute will soon come before an international tribunal. It is highly recommended that States reconcile their differences through mutual understanding and confidence-building measures to avoid escalation of disputes over military activities in the EEZ.

6.4.1 Agreements to Prevent Incidents at Sea

As political tensions kept rising during the Cold War, the USSR concluded a number of bilateral agreements with Western maritime powers to prevent incidents between their military entities at sea beyond the limit of the territorial sea.Footnote ²⁹⁷ These agreements were formulated to reduce misunderstanding between the parties and to promote safety at sea for all interested States.

In order to prevent the accidental outbreak of nuclear war in light of several close incidents between naval forces in the 1960s, the United States and the USSR concluded the 1972 Agreement on Prevention of Incidents on and over the High Seas (US-USSR Agreement), which came into force on the same day.Footnote ²⁹⁸ The US-USSR Agreement obligates the parties to ‘take measures to instruct commanding officers of their respective ships to observe strictly the letter and spirit of the International Regulations for Preventing Collision at Sea’ and the principles with respect to conducting operations at sea as recognised in the 1958 Convention on the High Seas.Footnote ²⁹⁹ Specifically, it provides detailed guidelines for preventing accidents on the high seas while conducting naval operations.Footnote ³⁰⁰ In an amendment made by an exchange of notes between the two States in 1998, the US-USSR Agreement applies to ‘waters outside the limits of the territorial sea’.Footnote ³⁰¹ Consequently, these operational guidelines are applicable to both parties’ navies, where each is operating in the other’s EEZ.

The USSR concluded similar bilateral agreements for the purpose of reducing provocative or risky behaviour of armed forces and military aircraft beyond the limit of the territorial sea with the United Kingdom in 1986,Footnote ³⁰² with Germany in 1988Footnote ³⁰³ and with France, Canada and Italy in 1989Footnote ³⁰⁴ (USSR Prevention of Incidents at Sea Agreements). It is notable that all of these agreements have adopted practical measures to assist the State parties in fulfilling their obligations, including the requirements for an annual meeting to review the implementation of the terms, and the use of mutually agreed special signals for communication or marks to be used by the ships and aircraft.Footnote ³⁰⁵

The USSR Prevention of Incidents at Sea Agreements suggest that, at least among contracting parties, all States have an unfettered right to conduct weapons exercises, naval manoeuvres and other military activities beyond the territorial sea, including in a foreign EEZ. Moreover, it is important for States to exchange information and clarify their intentions when conducting military activities, not out of a legal obligation of general international law but for good faith, political and security purposes, in order to promote mutual trust and avoid misunderstandings and thus reduce the chance of potential conflicts.

Since the end of the Cold War, China has been a consistent challenger to the military activities conducted by the United States within its EEZ through operational means.Footnote ³⁰⁶ By ‘recognizing the need to promote common understanding regarding activities undertaken by their respective maritime and air forces when operating in accordance with international law, including the principles and regimes reflected in the [UNCLOS]’, the United States and China concluded the Agreement on Establishing a Consultation Mechanism to Strengthen Military Maritime Safety in 1998 (US-China Agreement).Footnote ³⁰⁷ It establishes a stable channel for consultations between the two States consisting of three mechanisms, namely annual meetings, working groups of subject matter experts and special meetings for consulting on specific matters.Footnote ³⁰⁸ The US-China Agreement has played a momentous role in dealing with incidents between the two States. For instance, the two sides held several special meetings in Beijing after the April 2001 collision discussed earlier in the chapter, which led to an agreement on compensation, the release of the crew and the return of the EP-3 plane, resolving this incident without causing serious setbacks to the relationship between the United States and China.Footnote ³⁰⁹ In 2014, the two States signed two memoranda of understanding (MOUs) establishing voluntary confidence-building measures intended to manage risk, enhance mutual understanding and avoid miscalculation between the two militaries: the Notification of Major Military Activities MOU and the Rules of Behavior for Safety of Air and Maritime Encounters MOU.Footnote ³¹⁰ The actual value of the US-China Agreement and MOUs, however, might not have been fully realised, since it has not prevented conflicts from arising.Footnote ³¹¹ In particular, the bilateral dialogue has been interrupted by the tension in the South China Sea and the Taiwan Strait where both sides blame the other State of provoking actions that threat the stability of the region.Footnote ³¹²

It is noteworthy that an agreement to prevent an escalation of tensions between militaries at sea would have more influence if it was agreed to and obeyed by many State parties. In 2014, at the Western Pacific Naval Symposium, a series of biennial meetings of Pacific nations to discuss naval matters, naval chiefs of twenty-one States adopted a non-binding Code for Unplanned Encounters at Sea (CUES) that has been subsequently amended.Footnote ³¹³ CUES is a set of rules-of-the-road standardising safety protocols, basic communications and basic manoeuvring at sea for ships and aircraft to avoid misjudgement, misunderstanding and mismanoeuvring among navies.Footnote ³¹⁴ Despite of its non-binding nature, CUES may contribute to the improvement of good order at sea and prevent accidental conflicts should the navies follow these rules.

Given that the most controversial practice is between the coastal State that seeks to halt foreign military operations in its EEZ and other States that continue to conduct them, a bilateral agreement or arrangement to prevent conflicts and avoid escalatory events seems necessary and appropriate. An agreement to avoid accidents is one of the confidence-building mechanisms that enhances mutual knowledge and understanding of military activities at sea between the State parties, consequently reducing the possibility of conflict by accident, miscalculation, or failure of communication.Footnote ³¹⁵ These practices provide a functional framework for States to pay mutual respect to military uses of the sea, and should be implemented effectively and efficiently.

6.4.2 Regional Disarmament Efforts

The international community is moving steadily towards peace and security, including global nuclear non-proliferation and disarmament through strengthening political and legal frameworks.Footnote ³¹⁶ Global disarmament efforts affect the general acceptance and use of weapons at sea. States have adopted a number of regional arrangements and treaties that indicate their support for limiting the use of weapons at sea, particularly nuclear weapons, weapons of mass destruction and other strategic weapons.Footnote ³¹⁷ These regional frameworks not only apply to the territorial sea and the EEZ of the State parties but also extend to the high seas. These agreements should be compatible with UNCLOS without affecting the enjoyment of rights or the performance of obligations by States but, nevertheless, may to varying degrees affect the conduct of military activities involving nuclear-armed warships.Footnote ³¹⁸

The Antarctic Treaty was adopted in 1959 with the aim to reserve the Antarctic for peaceful purposes only and to promote scientific research.Footnote ³¹⁹ It covers the area south of 60° South latitude, within which State parties shall prohibit ‘any measures of a military nature, such as the establishment of military bases and fortifications, the carrying out of military maneuvers, as well as the testing of any type of weapons’.Footnote ³²⁰ The demilitarisation of the Antarctic has eliminated potential armed conflicts or military incidents arising from the complex territorial disputes in the region.Footnote ³²¹ By acceding to the Antarctic Treaty, State parties agreed to abolish the military use of the treaty area, including their frozen maritime zone claims.Footnote ³²² The Antarctic Treaty remains in force indefinitely, and as of 2024 has twenty-nine Consultative Parties and another twenty-eight Non-Consultative Parties that have no decision-making power.Footnote ³²³

The efforts of the littoral States to establish the Indian Ocean as a zone of peace date back to the 1970s as a response to the military rivalry between the United Kingdom, the United States and the USSR in the region.Footnote ³²⁴ This led to the adoption of UNGA Resolution 2832 (1971), which recognises this movement and declared the Indian Ocean, together with the air space above and the sea floor subjacent thereto, to be a ‘zone of peace’.Footnote ³²⁵ It called on all superpowers to enter into immediate consultations with the littoral States with a view to ‘halting the further escalation and expansion of their military presence’ and to remove ‘all bases, military installations and logistical supply facilities, the disposition of nuclear weapons and weapons of mass destruction and any manifestation of great Power military presence’ from the region.Footnote ³²⁶ It also called on States to make efforts to establish ‘a system of universal collective security without military alliances and strengthening international security through regional and other co-operation’.Footnote ³²⁷ The Ad Hoc Committee on the Indian Ocean was established in 1972 to study the implications of Resolution 2832 (1971).Footnote ³²⁸ However, these efforts did not stop the steady escalation of the arms race and the competitive military presence in the region.Footnote ³²⁹ On the contrary, the United States established a military base on the atoll of Diego Garcia, a British Indian Ocean Territory, in 1971 and maintains its presence to date.Footnote ³³⁰ Due to the non-participation of many military powers (especially France, the United Kingdom and the United States), the Ad Hoc Committee was not been able to embark on any discussions on practical measures to implement the declaration of a ‘zone of peace’ in the Indian Ocean.Footnote ³³¹ In recent years, given the changes in the political environment and security priorities in the region, the Ad Hoc Committee has discussed changing its mandate to address non-traditional maritime threats and challenges and continued to call for all permanent members of the Security Council and the major maritime users of the Indian Ocean to support its work.Footnote ³³²

States have also adopted several regional treaties that, broadly stated, prohibit the testing, use, manufacture, production or acquisition of nuclear weapons through establishing nuclear-free zones and nuclear weapon–free zones covering parts of Latin America and the Caribbean, the South Pacific, Southeast Asia, Africa and Central Asia.Footnote ³³³ For example, in the wake of the Cuban Missile Crisis in 1967, twenty-one Latin American States signed the multilateral Treaty for the Prohibition of Nuclear Weapons in Latin America (Treaty of Tlatelolco).Footnote ³³⁴ All State parties undertake the obligation to prohibit and prevent in their respective territories, including the territorial sea, the testing, use, manufacture, production, acquisition or any form of possession by any means whatsoever of any nuclear weapons.Footnote ³³⁵ Through Additional Protocol II, all five nuclear weapon States have committed themselves to respect the status of the nuclear-free zone and not use or threaten to use nuclear weapons against any State parties to the Treaty of Tlatelolco.Footnote ³³⁶ This Treaty created the first nuclear weapon–free zone, which promoted the development of nuclear non-proliferation within this region and beyond, and served as a model for four other nuclear weapon–free zones in the South Pacific (1985), Southeast Asia (1995), Africa (1996) and Central Asia (2006).Footnote ³³⁷ These zones have been recognised as contributing to ‘the security of members of such zones, to the prevention of the proliferation of nuclear weapons and to the goals of general and complete disarmament’.Footnote ³³⁸

In summary, States’ efforts to regulate military activities at the international level are limited to establishing guidelines to prevent misunderstandings and promote co-operation, and the only agreed prohibition is with regard to the use of nuclear weapons on a regional basis that are largely restricted to areas under the sovereignty of the contracting parties. This confirms that not only is there no general prohibition on conducting military activities in the EEZ under international lawFootnote ³³⁹ but also that States are unable to develop precise legal obligations to regulate such uses. In order to prevent further conflicts at sea, States must take further steps to build mutual trust, including the adoption of good practices for military activities at sea, especially in regions where such activities are most frequently challenged.