1. Introduction
In recent years, numerous cases brought before the International Court of Justice (ICJ or the Court) have related to matters of territory (including boundaries) and territorial sovereignty; settlement of disputes of this kind has, of course, always been a feature of the Court's work,Footnote 1 but they have come to predominate on the Court's General List. The trend might, perhaps, seem unexpected at first sight, in view of the long-established division of most of the world into state territories, and the availability of advanced technology for the fixing of accurate boundaries. However, even a long-established state may enjoy its sovereignty over territories that are a bit vague round the edges, or may be a party to long-standing territorial disputes, unresolved and sometimes appearing unresolvable. It should also not be overlooked that in many parts of the world, and until comparatively recent times, the concept of a state as having, and being defined by, established boundaries was by no means universally accepted: ethnic or tribal loyalties, for example, might have a more defining role,Footnote 2 and this may remain reflected in the definition – or lack of it – of a boundary.
In addition, although decolonization is a process that, for most purposes, may be regarded as having run its course, it left a legacy of territorial uncertainties or imprecisions. A boundary that was clearly enough defined during the colonial period, particularly when the territory on both sides of it was administered by the same colonial power, may come to cause difficulties when it separates two sovereign states, possibly markedly jealous of their territorial claims, and perhaps even not on good terms.Footnote 3
A further clue to the current importance of territorial disputes, some over apparently minimal areas, in current ICJ jurisprudence may be seen in a well-known factor that has come to make some odd bits of coastal territory much more important than they were before: the principle that ‘the land dominates the sea’, and thus ‘the terrestrial territorial situation that must be taken as starting point for the determination of the maritime rights of a coastal State’.Footnote 4 The exact point on a coastline at which an international boundary reaches the sea may in itself be of no, or limited, economic significance; but its determination may affect entitlement to a considerable maritime area. The presence of islands, rocks and similar features lying off the coasts may have to be taken into account; whether a given feature legally is or is not part of the ‘territory’ may substantially affect the coastal state's rights to seabed areas, the exploitation of which may of course bring very substantial revenues, broadly relative to the extent of the area of seabed or exclusive economic zone (EEZ) to which entitlement is shown.
A feature of territorial disputes to be noted also is that they require precision, completeness and finality in their settlement. Some inter-state disputes, particularly those of an essentially political nature, can be regulated on a general level so as to permit of relations in the relevant domain being carried on without friction, minor points being left unsettled, each party retaining its own view on the matter. But, increasingly in modern international relations, a territorial boundary generally needs to be complete and precise if it is to be useful, with no areas left vague; and these qualities may well be secured by a judicial or arbitral settlement.Footnote 5 At the same time, such a settlement remains ultimately a substitute for agreement,Footnote 6 and is itself based on the consent of the parties, either direct or through jurisdictional agreement. Yet there is a magic in the pronouncements of a court: this may explain why Burkina Faso, in the Territorial Dispute case between itself and Niger, urged the Court to include in its judgment determining the boundary a section of it which had already, before the proceedings were instituted, been the subject of agreement between the parties: the objective was ‘to endow this line with the force of res judicata’.Footnote 7
For the purposes of this study, the chronological period referred to will be (purely for convenience) from the opening of the twenty-first century to the present day, with the inclusion also of the decision in Kasikili/Sedudu Island in 1999,Footnote 8 and occasional references to earlier decisions (Apart from these decided cases, there are no less than nine cases pending on the Court's General List involving similar questions related to territoryFootnote 9 ). No attempt will be made to analyze every one of the cases individually, nor to mention every question arising; they are far too many and too complex. The intended purpose is limited in scope: to offer some classification of territorial questions arising in this context, to indicate some salient features, and a number of considerations affecting their legal resolution.
Despite the lack of a strict rule of stare decisis, the Court's jurisprudence is generally consistent, and it frequently cites earlier judgments in support of its decisions. The jurisprudence on territorial matters is no exception to this. It would therefore not be a straightforward matter to analyze the case law in terms of its character as continuative as opposed to innovative, and it has been thought best simply to note precedents and individualities in passing.
Cases relating solely to the definition of a maritime boundary – unless they involve coastal questions, as explained above – are not within the scope of the present study, which is directed to the limits of land territory; what the Court has called ‘State borders, an expression which does not easily apply to areas beyond territory, including the territorial sea’.Footnote 10 While the territorial sea is (as its name implies) for some purposes part of the territory, and subject to the sovereignty of the coastal state, in general areas of seabed over which the coastal state has rights are not. More relevant for present purposes is that the law governing entitlement to such areas, and the boundaries between them, is quite distinct from the more long-established law governing acquisition of, and sovereignty over, land territory, and land boundaries.Footnote 11
2. Definition of the dispute
If a disputed question of territory comes before the Court, two preliminary questions may arise: first, whether it should be qualified as a boundary dispute or as a territorial dispute; secondly at what date the dispute took definitive form or ‘crystallized’.
The first question may be worded in several ways, e.g., in Burkina Faso/Mali, the Court distinguished ‘frontier disputes’ (or ‘delimitation disputes’) from ‘disputes as to attribution of territory’.Footnote 12 The first places the emphasis on establishing the position of a dividing line, the second on the areas divided by the line; but as the Court observed in 1986, the matter is ‘not so much a difference in kind’ as ‘a difference of degree as to the way the operation in question is carried out’.Footnote 13 Which terminology should be used must, it seems, depend on circumstances;Footnote 14 or possibly on the terminology chosen by the applicant state, which may or may not signify any clear intended distinction. In the case entitled ‘Territorial Dispute’ between Libya and Chad, however, the parties attached some importance to the question whether this terminology, or rather ‘boundary dispute’, was appropriate. Their respective viewpoints were the consequence of the nature of their legal contentions. Libya found ‘territorial dispute’ appropriate because it ‘proceeds on the basis that there is no existing boundary, and asks the Court to determine one’.Footnote 15 Chad's preference for ‘boundary dispute’ was ‘on the basis that there is an existing boundary [defined by a Treaty of 1955], and [it] asks the Court to declare what that boundary is’.Footnote 16
At the beginning of its judgment the Court placed on record this situation, but gave no indication as to which approach might be correct.Footnote 17 When summing up at the close of its decision, it indicated that the dispute (and thus the boundary) ‘is conclusively determined by [the] Treaty’ of 1955, but then brushed the point aside: ‘whether [the dispute be] described as a territorial dispute or as a boundary dispute’.Footnote 18 While there is some logic in Libya's position, arguably a dispute over where a boundary should be is as much a ‘boundary dispute’ as where it is. Ultimately, the real concern of states in contexts of this kind is to avoid an opponent taking factitious points along the lines of ‘by calling it a boundary dispute, you admit that there is an existing boundary!’
Can the Court lay down the position of a boundary where there has hitherto not been one? International law has nothing to say on where a particular boundary should be,Footnote 19 merely that the boundary is where the parties agree that it is.Footnote 20 The parties can, however, similarly by agreement, empower the Court to make the determination, according to defined criteria, or even at its discretion. Normally the jurisdictional instrument, usually a Special Agreement, will give broad enough powers for this;Footnote 21 but a problem could conceivably arise if the jurisdictional basis were, e.g., a narrowly-drafted acceptance of the ‘optional clause’.
In Pulau Ligitan and Pulau Sipadan there was controversy over the meaning of a treaty of 1891, which had stated that ‘the boundary line’ (already defined in the treaty) ‘shall be continued along’ a defined parallel of latitude; according to one interpretation, this continuation would only run across a particular territory (Sebatik Island) and then stop; according to the other, it would continue further, out to sea, so as to attribute a number of islands to the one party or the other. The Court considered that:
a “boundary”, in the ordinary meaning of the term, does not have the function that Indonesia attributes to the allocation line that was supposedly established by [the Treaty] out to sea beyond the island of Sebatik, that is to say allocating to the parties’ sovereignty over the islands in the area.Footnote 22
This is a distinction that makes sense: a ‘boundary line’ is surely, in general usage, a line along which the sovereignty of one state actually encounters, continuously, the sovereignty of the other.
A procedural principle in dispute settlement that has come to be transposed to the field of territorial disputes involves the ascertainment of the date on which the dispute ‘crystallized’.Footnote 23 The procedural significance of the term has been in determining the existence of a dispute, in effect whether it has been sufficiently defined in exchanges between the parties for it to be ‘ripe’ for settlement by the Court.Footnote 24 Its more recent application results from the circumstance that territorial disputes often involve quite long periods when there are competing interests in a territory, which may be strengthened or weakened by action or inaction as time passes.Footnote 25 At some point the parties, being or becoming aware of each other's claims, are no longer each acting in relation to the territory simply in the belief that they are exercising an entitlement, but in order to reinforce a claim. It is at that moment that the legal situation becomes ‘crystallized’. It is by reference to this date, also referred to as the ‘critical date’,Footnote 26 that the judge can distinguish those acts which should be taken into consideration for the purpose of establishing or ascertaining sovereignty over a disputed territory. Acts occurring after that date, as the Court said in Pedra Blanca, ‘are in general meaningless for that purpose, having been carried out by a State which, already having claims to assert in a legal dispute, could have taken those actions strictly with the aim of buttressing those claims’.Footnote 27
Another way of expressing the concept, also employed in the same case, is to say that the Court:
cannot take into consideration acts having taken place after the date on which the dispute between the Parties crystallized unless such acts are a normal continuation of prior acts and are not undertaken for the purpose of improving the legal position of the Party which relies on them.Footnote 28
The distinction is not entirely convincing: it suggests that any action taken after the crystallization is to be presumed to have the aim of ‘buttressing’ the claim. If an action on the disputed territory otherwise qualifies as an effectivité, according to the criteria to be discussed in Section 6 below, it will add to the weight of evidence in favour of the actor's claim, and thus necessarily ‘improve’ its ‘legal position’.Footnote 29
What, for this purpose, precisely constitutes ‘crystallization’ of a dispute? In Pulau Ligitan and Pulau Sipadan the parties agreed that, in respect of these two named islands, ‘the dispute crystallized in 1980, when Singapore and Malaysia formally opposed each other's claims . . .’Footnote 30 In the Territorial and Maritime Dispute between Nicaragua and Colombia, the Court attributed crystallizing effect to a particular diplomatic Note as a ‘manifestation of a difference of views between the Parties regarding sovereignty over certain maritime features’.Footnote 31
In the case of a dispute concerning a former colonial territory, the same concept of a ‘critical date’ appears, with a similar ‘freezing’ effect on the significance of acts in relation to the territory. This date will normally be the date of accession to independence, in the sense that the intercolonial boundary will at that moment become the boundary between independent states.Footnote 32 As was pointed out by Judge Bennouna in the Frontier Dispute, the Court may, however, ‘have to clarify that evidence by reference to material facts subsequent to independence’.Footnote 33
3. What is sovereign territory? Islands and low-tide elevations
The existence of different systems of law governing territorial sovereignty and maritime rights requires the distinction to be clear between what is land territory and what is not.Footnote 34 Where the territorial boundary arrives at a point on a straightforward coast, lines for allocation of maritime spaces depend simply on that point.Footnote 35 Yet, as mentioned above, title to small pieces of land in key positions may influence its localization, so that apparently disproportionate attention may be paid to disputes over trivial ‘bits’ of territory: islands, rocks and other coastal features.Footnote 36
In this context, the key question is not whether a small maritime feature is or is not under the sovereignty of the coastal state, but whether it is or is not an ‘island’, and therefore qualifies not merely as a portion of land territory, but as one that generates rights over the neighbouring seabed. The accepted definition is that of the United Nations Convention on the Law of the Sea (UNCLOS) Article 121(1): ‘An island is a naturally formed area of land, surrounded by water, which is above water at high tide’.Footnote 37 That Article goes on to add that ‘Rocks which cannot sustain human habitation or economic life of their own shall have no exclusive economic zone or continental shelf’. The definition thus does not relate to the size of the land areaFootnote 38 – recent cases have involved objects with minimal dimensions – but to continued presence at high tide, and to the possibility of habitation or economic life. But may features lacking these qualities yet be part of a state's territory?
The legal nature of low-tide elevations was examined by the Court in Maritime Delimitation and Territorial Questions between Qatar and Bahrain. After first observing that ‘a coastal State has sovereignty over low-tide elevations which are situated within its territorial sea, since it has sovereignty over the territorial sea itself’,Footnote 39 it found that neither international treaties nor international practice answered ‘the question whether [other] low-tide elevations can be considered to be “territory”’; it continued:
It has never been disputed that islands constitute terra firma, and are subject to the rules and principles of territorial acquisition; the difference in effects which the law of the sea attributes to islands and low-tide elevations is considerable. It is thus not established that in the absence of other rules and legal principles, low-tide elevations can, from the viewpoint of the acquisition of sovereignty, be fully assimilated with islands or other land territory.Footnote 40
In Sovereignty over Pulau Ligitan and Pulau Sipadan, the parties asked the Court ‘to determine whether sovereignty over’ these features belonged to the one state or the other;Footnote 41 they thereby recognized that in their shared view these were portions of land territory capable of being subject to sovereignty, that is to say, islands. The Court characterized Ligitan as ‘a very small island’ and Sipadan as ‘a small island’.Footnote 42 The case of Pedra Branca, Pulau Batu Puteh, Middle Rocks and South Ledge, between Malaysia and Singapore, involved a wider variety of features: Pedra Branca, or Pulau Batu Puteh, is an island large enough to bear a lighthouse, but little else; the other features named are clusters of small rocks.Footnote 43 Middle Rocks was a feature regarded by both parties as permanently above water, and as having been under the sovereignty of the Sultan of Johor, thus as an island, part of his land territory.Footnote 44 The status of South Ledge, on the other hand, was disputed, but it was regarded by the Court as a ‘low-tide elevation’.Footnote 45 The Court again left open the question whether such an elevation outside territorial waters could be the subject of sovereignty; this it was able to do since it found that South Ledge was necessarily within the territorial waters of the one party or the other.Footnote 46
In Territorial and Maritime Dispute (Nicaragua v. Colombia), the maritime features in dispute were ‘the Alburquerque Cays, East-Southeast Cays, Roncador, Serrana, Quitasueño, Serranilla and Bajo Nuevo’.Footnote 47 The Court recalled the established rules that islands, however small, are capable of appropriation, and that the coastal state has sovereignty over low-tide elevations within its territorial sea,Footnote 48 and noted that the parties agreed that all the features were legally islands, except for certain features of Quitasueño. Only one such feature (QS32) proved relevant, and the debate therefore focused on its presence or absence above water at high tide, and on what tidal model was to be applied for the meaning of ‘high tide’. The Court eventually ruled that ‘no matter which tidal model is used, it is evident that QS 32 is above water at high tide’.Footnote 49
4. Territorial attribution: From whence may a state derive its territory?
International law recognizes a number of sources from which a state may have derived the whole or part of its territory.Footnote 50 The classic enumeration of the modes of acquisition of territorial sovereignty comprises accretion, cession, succession, conquest, effective occupation, and prescription.Footnote 51 Both the territory the state was born with, as it were, at the moment of independence, and any territory acquired subsequently, must be attributable to one of these modes. For long-established states, the original territory is practically a ‘given’; yet even for these there may be neglected boundary problems raising questions of title.Footnote 52
(1) A purely physical means of acquisition of territory is the growth or extension of the land territory by natural means: accretion. A difficulty in respect of these processes is that their effects may not be lasting: what nature gave, nature may take away again (avulsion). In Territorial and Maritime Dispute between Nicaragua and Honduras in the Caribbean Sea (Nicaragua v. Honduras), it was noted that:
[a] claim was also made during the oral proceedings by each Party to . . . the island in the mouth of the River Coco. For the last century the unstable nature of the river mouth has meant that larger islands are liable to join their nearer bank and the future of smaller islands is uncertain. Because of the changing conditions of the area, the Court makes no finding as to sovereign title over islands in the mouth of the River Coco.Footnote 53
This was an important aspect of the dispute because of the impact of the islands on the position of maritime delimitation lines. The Court merely held that the islands were inappropriate as a reference point: it did not say or imply that they were not sovereign territory of a coastal state, merely because they were unstable.
(2) Cession of territory by another state: this must necessarily be by agreement,Footnote 54 and sometimes occurs for the adjustment of a frontier (see for example the planned exchange of territories for purposes of the works in Gabčíkovo/Nagymaros Project Footnote 55 ). Cases of acquisition of territory by colonial powers from the local indigenous authorities may sometimes fall into this category, though such transactions may alternatively have been regarded from a colonizing point of view as in effect annexation of terra nullius.Footnote 56
A formal act of cession is not essential; sovereignty may be found to have passed through conduct, amounting to tacit acquiescence. In Pedra Blanca/Pulau Batu Puteh Land, Island and Maritime Frontier Dispute, the Court held that:
Under certain circumstances, sovereignty over territory might pass as a result of the failure of the State which has sovereignty to respond to conduct à titre de souverain of the other State or, as Judge Huber put it in the Island of Palmas case, to concrete manifestations of the display of territorial sovereignty by the other State (Island of Palmas Case (Netherlands/United States of America), Award of 4 April 1928, RIAA, Vol. II, p. 839). Such manifestations of the display of sovereignty may call for a response if they are not to be opposable to the State in question. The absence of reaction may well amount to acquiescence. The concept of acquiescence “is equivalent to tacit recognition manifested by unilateral conduct which the other party may interpret as consent . . .” (Delimitation of the Maritime Boundary in the Gulf of Maine Area (Canada/United States of America), Judgment, I.C.J. Reports 1984, p. 305, para. 130). That is to say, silence may also speak, but only if the conduct of the other State calls for a response.Footnote 57
It is the conduct of both parties that is relevant: in Pedra Blanca/Pulau Batu Puteh, the Court found that there had been ‘a convergent evolution of the positions of the Parties regarding title’ to those territories, as a result of which ‘by 1980 sovereignty . . . had passed to Singapore.’Footnote 58
Cession, while it may thus be tacit, is always treated as the considered act of the state having sovereignty; it does not just happen unnoticed, as might be possible in the case of prescription (see below).Footnote 59
(3) SuccessionFootnote 60 – transfer from a former sovereign to a subsequent sovereign – is distinguishable from cession in the sense that it is not necessary to show an intentional transfer (thought this may have been effected), but simply that the claimant ‘inherited’ the territory from a former sovereign, either as universal successor, or in respect of certain territories of which the subject of the dispute can be shown to have been part. Such a succession is most frequently met with in cases of accession to independence, with the application of ‘the principle of the succession of States to the frontiers inherited from colonialism’, involving ‘the principle of the intangibility of such frontiers, also known as the principle of uti possidetis juris’.Footnote 61 The legal questions arising in such a case usually concern the original cession or occupation by the colonial power, and are examined in Section 7 below).
More complex examples of an inherited title outside the context of decolonization are in those of Indonesia and Malaysia relating to Pulau Ligitan and Pulau Sipadan.Footnote 62 Indonesia's claim was comparatively simple: transfer from the Sultan of Bulungan to the Netherlands to Indonesia; that of Malaysia involved considerably more successive transactions. The Court was not convinced by either claim (and decided the case on the basis of effectivités); it indicated that what was required was ‘an uninterrupted series of transfers of title from the alleged original title-holder . . . to . . . the present one’.Footnote 63
(4) Acquisition by conquest or debellatio, once a regular international practice, is now excluded by the generally recognized illegality of the use of force.Footnote 64 Technically this might be seen as forced cession, annexation, or succession in cases of total conquest. In the Palestine Wall case, ICJ clearly implied that annexation would now be unlawful:
The Court considers that the construction of the wall and its associated régime create a “fait accompli” on the ground that could well become permanent, in which case, and notwithstanding the formal characterization of the wall by Israel, it would be tantamount to a de facto annexation.Footnote 65
(5) Occupation:Footnote 66 since this means of acquiring sovereignty is restricted to occupation by a state of unclaimed territory (terra nullius), it is primarily of interest when a title established in colonial times is under examination.Footnote 67 Title is claimed as deriving from a predecessor, usually a colonizing state, which is said to have taken over territory that at the time fell within that category. Such a present-day title may therefore derive from occupation which was legal at the time, in accordance with the principle of intertemporal law.Footnote 68
The expression ‘terra nullius’ was a legal term of art employed in connection with ‘occupation’ as one of the accepted legal methods of acquiring sovereignty over territory. ‘Occupation’ being legally an original means of peaceably acquiring sovereignty over territory otherwise than by cession or succession, it was a cardinal condition of a valid ‘occupation’ that the territory should be terra nullius – a territory belonging to no-one – at the time of the act alleged to constitute the ‘occupation’.Footnote 69 In the view of the Court, therefore, a determination that Western Sahara was a ‘terra nullius’ at the time of colonization by Spain would be possible only if it were established that at that time the territory belonged to no-one in the sense that it was then open to acquisition through the legal process of ‘occupation’. Footnote 70
The counterpart to the concept of res nullius is that of the uti possidetis juris, in the sense that a state attaining independence will inherit the territory in the legal possession of the predecessor state, including such areas as may at one time have been res nullius; this will be discussed in Section 7 below.
Unclaimed territory is not, however, necessarily terra nullius. An unusual situation arose in the Burkina Faso/Niger case, inasmuch as the boundary lines claimed by each of the parties left a triangular area unclaimed by either of them. They did not, however, suggest that this area was terra nullius, since in fact each party attributed it to the other.Footnote 71 The Court responded by observing that:
the principle whereby the Court does not rule ultra petita does not prevent it, in this case, from attributing that territory to one or the other Party, since the Special Agreement entrusts it with the task of fully determining the course of the frontier in the area.Footnote 72
In its terms, however, this resolves merely the procedural issue;Footnote 73 but since the area in question was an enclave, occupation by any third state, even if a theoretical possibility, was excluded for practical reasons.
(6) Acquisition of territory previously under existing sovereignty of another state, the sovereignty of which has become displaced, by a process referred to as acquisitive prescription. The existence of this concept in international law is not universally accepted. The Court has never upheld a claim on that basis, though it was recognized as a possibility in the Eritrea/Yemen arbitration.Footnote 74 It was relied on by Namibia in Kasikili/Sedudu Island, and while this claim was disputed, and not upheld, the parties were agreed as to the conditions that needed to be fulfilled. The Court noted the conditions as indicated by Namibia and accepted by Botswana:
[F]our conditions must be fulfilled to enable possession by a State to mature into a prescriptive title: “
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1. The possession of the . . . state must be exercised à titre de souverain.
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2. The possession must be peaceful and uninterrupted.
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3. The possession must be public.Footnote 75
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4. The possession must endure for a certain length of time.”Footnote 76
The Court found that these conditions, in particular the requirement of possession à titre de souverain, had not been fulfilled, and was thus able to decline to consider ‘the status of acquisitive prescription in international law’.Footnote 77
The last condition highlights an essential difference between prescription in national legal systemsFootnote 78 and the phenomenon bearing the same name in international law. National systems may, and generally do, lay down, as a requirement, the passage of a specific term of years during which the title-holder's rights have been usurped: once such a term has expired without an act by that title-holder interrupting it, a prescriptive title is acquired. In international law, the judge must decide how long a period is sufficient.
Prescription seems to have been in the background to the decision in Pedra Blanca/Pulau Batu, though the term was not used in the key paragraphs of the judgment;Footnote 79 Judges Abraham, SimmaFootnote 80 and DugardFootnote 81 recognized its existence and relevance. The case was decided on the basis of a finding that sovereignty over the territory passed from Malaysia to Singapore, as a result of conduct of each of the two states and their predecessors, including the failure on the Malaysian side to react to certain conduct of the Singapore side.Footnote 82 There appears to be a narrow dividing line between such a conclusion (transfer apparently by acquiescence) and a conclusion in favour of prescription. The concepts would be more clearly distinguishable if the essence of prescription were that, if the conditions above are fulfilled, the established title of one state were extinguished and replaced by a new title of the other state, rather than being transferred; but this borders on speculation.
(7) There was a claim by Nigeria in Land and Maritime Boundary between Cameroon and Nigeria to acquisition of territory by ‘historical consolidation’: the meaning of this in relation to land territory is, however, obscure.Footnote 83 The Court was very doubtful as to the existence of the concept: it referred to the theory as ‘highly controversial’, and considered that ‘it cannot replace the established modes of acquisition of title under international law’; in any event it did not uphold the claim on the facts.Footnote 84 A different view was taken by Judges Koroma and Ajibola,Footnote 85 who considered that this was a recognized basis for asserting territorial sovereignty.
The term ‘consolidation’ may be ill-chosen, as it implies the previous existence of something to be consolidated, strengthened; this would suggest that there has to be a pre-existing title, not merely a claim, to become consolidated; but this may be reading too much into the word.
A state may thus have sovereignty over a particular territory on the basis of one or other of these grounds; a separate question is how it demonstrates that this is so. A claim to territorial sovereignty may be substantiated essentially in one of two ways: by showing title,Footnote 86 or by demonstrating the existence of relevant acts on the ground; sovereignty is as sovereignty does. Such acts are classified as effectivités. The essential difference between titles and effectivités as bases for a claim to sovereignty over territory would seem to be that a title constitutes a conveyance or recognition of such sovereignty on the part of one or more international actors with an interest in the matter. Effectivités, on the other hand constitute an assertion of sovereignty by the state performing them, and the role – an essential one – of other interested parties is essentially one of acquiescence or recognition, often reluctant or even unintended.
5. Titles
The Court has defined a ‘territorial title’ as being ‘a document endowed by international law with intrinsic legal force for the purpose of establishing territorial rights’.Footnote 87 It may establish the territorial rights directly of a party to the dispute, or those of a predecessor, claimed to have passed by assignment or on the basis of the uti possidetis juris. The title should be such as to identify clearly the territory to which it relates. A treaty is an evident example; and even signed but non-ratified treaties may constitute such a title, inasmuch as they ‘may constitute an accurate expression of the understanding of the parties at the time of signature’.Footnote 88 Other examples are: a Joint Declaration by two colonial powers defining the boundary between their territories (the 1919 Milner-Simon Declaration, invoked in Cameroon/Nigeria Footnote 89 ); an arrêté issued by the Governor-General of a colony;Footnote 90 and similar bilateral or unilateral instruments emanating from colonial powers.
5.1. Treaties as titles
A treaty may require to be examined in a dispute involving territory if it is relied on as a title, that is to say as constituting a cession or other acte juridique, or if it is concluded between two neighbouring states, with the purpose of defining a territorial boundary, and a question arises over its interpretation.Footnote 91 In the latter case, the treaty-dispute does not, strictly speaking, necessarily involve the body of international law concerning boundaries: the boundary has already been fixed by treaty, and the questions that have arisen, and have been referred to the Court, relate to the correct interpretation of that treaty. At least in theory, the only law to be applied will be the law of treaties, specifically the rules governing interpretation.Footnote 92 If the application of those rules does not resolve an ambiguity or uncertainty, international law as to the operation of territorial titles contains no rule to determine sovereignty. Is it then legitimate to resort to examination of, for example, effectivités? This of course involves abandoning the initial premise, that the treaty determined the boundary.
The problem arose in Territorial and Maritime Dispute between Nicaragua and Colombia, in which the Court, having found the material available ‘inconclusive’ on the question whether the disputed features were or were not part of the ‘San Andrés Archipelago’ referred to in a 1928 boundary treaty, concluded that:
In view of the above, in order to resolve the dispute before it, the Court must examine arguments and evidence submitted by the Parties in support of their respective claims to sovereignty, which are not based on the composition of the Archipelago under the 1928 Treaty[,]
namely, the effectivités invoked by the parties.Footnote 93 This was strongly (and, it is suggested, correctly) criticized by Judge Abraham, for whom ‘the Court commits a serious legal error: it fails, without valid justification, to rule on the interpretation of the 1928 Treaty’.Footnote 94
In Territorial Dispute (Libyan Arab Jamahiriya/Chad), there were a number of relevant treaties concluded between the predecessors in title of the two parties; Libya's contention was that these had not in fact resulted in complete frontiers, but that there were unsettled boundaries; the Court rejected this view, essentially on the ground that by the most recent treaty cited, Libya had ‘recognized’ that the frontiers ‘were those that result’ from the various treaties.Footnote 95
Another case in which a treaty between the parties constituted a major element, but was not, alone and of itself, determinative, was that of Pulau Ligitan and Pulau Sipadan (Indonesia/Malaysia). The treaty invoked was a Convention of 1891 between Great Britain and the Netherlands, the claim of Indonesia being based on succession to the Netherlands in this respect. The reason why, after discussion of the interpretation of the treaty, and of the claim of succession to it, it was not relied on in the Court's decision was simply because it was held to be limited in geographical extent, so as not to apply to the islands the subject of the dispute. That dispute therefore was determined on the bases of other considerations, of territorial law, to be considered below.
If the Court is asked to determine the course of a boundary on the basis of a treaty, that is to say, an agreement between the parties, what, if any, is the relevance of the legal considerations that induced the parties to conclude that agreement? In the Libya/Chad case just referred to, the Court observed that:
It will be evident from the preceding discussion that the dispute before the Court . . . is conclusively determined by a Treaty to which Libya is an original party and Chad a party in succession to France . . . Hence there is no need for the Court to explore matters which have been discussed at length before it such as the principle of uti possidetis and the applicability of the Declaration adopted by the Organization of African Unity at Cairo in 1964.Footnote 96
In Territorial Dispute between Burkina Faso and Niger, the relevant agreement defined the course of the intended boundary, but the Court was requested to determine its precise course; the agreement identified a legal text (a French arrêté) of the colonial period as point of reference. The dispute was thus similarly ‘conclusively determined’ by the agreement, yet the parties themselves had clearly regarded the principle of uti possidetis iuris as governing, either in itself or as having been invoked by the agreement; but the boundary specified was simply consensual. Judge Yusuf, in a powerfully argued separate opinion, contended that, as in the Libya/Chad case, the agreement alone should be referred to, and that ‘[t]he Judgment should have clearly recognized that uti possidetis juris and “droit d'outre-mer” had no effective role to play in this case’.Footnote 97 The logic of this position must be recognized; yet an agreement may need to be interpreted before it can be applied, and what was in principle ‘behind’ the agreement may have to be brought out and examined for the purposes of such interpretation.Footnote 98
The Court may, of course, find that the treaty did not settle the matter, and provided that it is asked, and thus given jurisdiction, generally to determine the boundary,Footnote 99 it may apply general law; this may involve an appeal to effectivités (Pulau Ligitan and Pulau Sipadan),Footnote 100 or parties may raise other issues, as for example the appeal to prescription in Kasikili/Sedudu Island.
Thus far we have been considering the role of an international treaty invoked as having a dispositive role, i.e., as effecting or having effected a transfer of sovereignty, or other rights, from one state to another; but a treaty – even unratified – may also be relevant simply as evidence of recognition of the rights asserted by a state over a territory. In Maritime Delimitation and Territorial Questions between Qatar and Bahrain, the Court attributed value of this kind to an unratified Treaty of 1913 as ‘represent[ing] evidence of the views of Great Britain and the Ottoman Empire as to the factual extent of the authority of’ the then ruler of Qatar in relation to Zubarah, and the exclusion of the Sheikh of Bahrain from any authority there.Footnote 101 The Court noted that ‘signed but unratified treaties may constitute an accurate expression of the understanding of the parties at the time of signature’.Footnote 102
5.2. Maps
While a map generally serves the purpose of identification of the territory and its boundaries, the Court has emphasized that a map, in and of itself, does not constitute a legal title: maps may have legal force as falling into ‘the category of physical expressions of the will of the State or States concerned’.Footnote 103 The Chamber seised of the Frontier Dispute (Burkina Faso/Mali) noted that some maps may constitute such expressions, ‘for example, when maps are annexed to an official text of which they form an integral part’; otherwise, ‘they are only extrinsic evidence of varying reliability or unreliability’.Footnote 104
In Pedra Blanca, the Court quoted with approval a statement in the Eritrea/Ethiopia case, that a map ‘stands as a statement of geographical fact, especially when the State adversely affected has itself produced and disseminated it, even against its own interest’.Footnote 105 Other factors relevant to the value of maps are: the neutrality of their sources towards the dispute;Footnote 106 the purpose for which they were prepared;Footnote 107 and the extent to which the territory was known and administered at the time the map was prepared, so that it can be taken to be based on reliable information.Footnote 108 In the Frontier Dispute between Burkina Faso and Niger, there had been an agreement between the parties that ‘the principle of the intangibility of boundaries inherited from colonization’ should be applied by reference to a French arrêté of the colonial period, and if this text should ‘not suffice’, the course of the boundary should be as shown on a specified map issued by the French Institut géographique national. The Chamber seised of the case noted that while the map was ‘not an official document’, it was supposed to reflect ‘the colonial effectivités at the critical date’; but the effect of the parties’ agreement was that ‘the frontier line drawn on the IGN map must be referred to on a subsidiary basis even if it does not correspond to those effectivités’.Footnote 109 The Chamber apparently did not feel free simply to take the IGN map line as an agreed line, and to disregard the whole question of its relation to the colonial effectivités. In the Territorial and Maritime Dispute (Cameroon/Nigeria) a mere sketch-map prepared by colonial officials served to interpret a reference in a document of title (the 1930 Thomson-Marchand Declaration).Footnote 110
Maps again were relied on in the Territorial and Maritime Dispute (Nicaragua/Colombia), in which the Court cited the classic dictum in the Burkina Faso/Mali case (above). The Court concluded that ‘although the map evidence in the present case is of limited value, it nevertheless affords some measure of support to Colombia's claim’.Footnote 111
6. Effectivités
The essence of the concept of effectivités was defined in Territorial and Maritime Dispute (Nicaragua/Honduras) in the following terms: ‘A sovereign title may be inferred from the effective exercise of powers appertaining to the authority of the State over a given territory’;Footnote 112 the Court there also repeated the terms in which its constituent elements were expressed, long before the term effectivités itself came into judicial use, by the Permanent Court:
a claim to sovereignty based not upon some particular act or title such as a treaty of cession but merely upon continued display of authority, involves two elements each of which must be shown to exist: the intention and will to act as sovereign, and some actual exercise or display of such authority.Footnote 113
The PCIJ also noted that a circumstance to be taken into account was ‘the extent to which sovereignty is also claimed by some other Power’.Footnote 114
It is analogous activity that is recognized as leading to acquisition of sovereignty over terra nullius, in other words the process of occupation, as described above. In that situation, the acts relied on are not usually referred to as effectivités, but must possess much the same attributes. It is also possible that rival claims are made by two states to the same territory, both based simply on alleged exercise of sovereign authority there. The most likely scenario is, however, that one claimant state asserts a title, as defined above, and the other alleges that, by its own activities in the territory, it has defeated that title and obtained sovereignty by implied cession, or acquiescence, or acquisitive prescription.Footnote 115
The relationship between titles and effectivités was defined by the Court in its 1986 decision in Frontier Dispute (Burkina Faso/ Mali):
[1] Where the act corresponds exactly to law, where effective administration is additional to the uti possidetis juris, the only role of effectivité is to confirm the exercise of the right derived from a legal title. [2] Where the act does not correspond to the law, where the territory which is the subject of the dispute is effectively administered by a State other than the one possessing the legal title, preference should be given to the holder of the title. [3] In the event that the effectivité does not co-exist with any legal title, it must invariably be taken into consideration. [4] Finally, there are cases where the legal title is not capable of showing exactly the territorial expanse to which it relates. The effectivité can then play an essential role in showing how the title is interpreted in practice.Footnote 116
If one claimant to a territory is relying on an ancient title, and the other on an acquisition of that territory by occupation (case [2]), each has the burden of proof of its assertions; but if neither proof is satisfactory, is there a presumption, one way or the other, to fall back on? In Pedra Blanca, a conflict of this kind presented itself, and each party insisted that the other had the burden of proof. The Court restated the principle that ‘a party which advances a point of fact in support of its claim must establish the fact’,Footnote 117 but apparently found that this did not resolve the problem. It seems then to have proceeded on an unavowed conception of a claim to a title as a positive, and that of occupation of terra nullius as a negative, with the consequence that the claimant relying on title has an initial burden of proof.Footnote 118 If no title is shown (either in the claimant or in a third state), and effectivités can be shown, then previous status as terra nullius may be presumed – but of course occupation still has to be demonstrated and proved by evidence. In either event, there must be (i) the intention and will to act as sovereign; (ii) some actual exercise or display of authority; and these must be assessed in relation to (iii) the extent to which acquiescence can be shown by any other state claiming sovereignty.
A common feature of cases involving territorial claims is therefore examination by the Court of what each of the disputing states actually did in relation to the territory: sovereignty is as sovereignty does – and sometimes it need do very little. In Nicaragua/Honduras, the Court cited the Eastern Greenland opinion as to the relevance of ‘the extent to which sovereignty is also claimed by some other Power’, and noting that:
It is impossible to read the record of the decisions in cases as to territorial sovereignty without observing that in many cases the tribunal has been satisfied with very little in the way of the actual exercise of sovereign rights, provided that the other State could not make out a superior claim. This is particularly true in the case of claims to sovereignty over areas in thinly populated or unsettled countries.Footnote 119
However, if the nature of the activities required to establish occupation of terra nullius, on the one hand, or to defeat an existing title, on the other, is closely similar, the process at work differs. In Land and Maritime Boundary (Nigeria/Cameroon), the Court, after noting the existence of some Nigerian activities à titre de souverain, pointed out that ‘as there was a pre-existing title held by Cameroon in this area . . . the pertinent legal test is whether there was thus evidenced acquiescence by Cameroon in the passing of title from itself to Nigeria’.Footnote 120 Similarly, the activities of the title-holder are also only relevant as indicating acquiescence or the lack of it.Footnote 121
In the Frontier Dispute (Benin/Niger), both parties relied on effectivités attributed to the pre-independence authorities,Footnote 122 including ‘the provision of licences for grazing, fishing and tree-felling, as well as the levying of taxes, periodic sanitary control of livestock, military patrolling and police activities’.Footnote 123 Another case in which the parties relied on a variety of effectivités was that of the Territorial and Maritime Dispute (Nicaragua/Honduras). The effectivités were grouped in the decision under the following headings: Legal and administrative control; Application and enforcement of civil and criminal law; Regulation of immigration; Regulation of fishing activities; Naval patrols; and Public works.Footnote 124 It was this last group that proved decisive (specifically, the erection on the disputed islands of a geodetic antenna in the context of oil exploration activities).Footnote 125
In Pulau Ligitan and Pulau Sipadan, each party claimed a treaty-based title, and invoked effectivités simply by way of confirmation; but the Court did not accept either of the alleged titles, and therefore considered the effectivités ‘as an independent and separate issue’.Footnote 126 The effectivités on which the Court based its decision were not very substantial, confirming the Eastern Greenland dictum cited above, to the effect that if there is no title that can be relied on, very little activity will be sufficient to be recognized as effectivités; perhaps less on the basis of their own merit than on the basis that certainty is better than the opposite, and the Court's role as a deciding body: sit finis litium.Footnote 127 Also in the Frontier Dispute (Benin/Niger) the Court noted that in one sector of the boundary ‘the effectivités relied on by the Parties are relatively weak’; this, however, after having decided that a boundary could be discerned without examining the effectivités.Footnote 128
The mere long-standing presence on the territory of nationals of the claimant state does not rank as an effectivité: it is essential that the occupation was à titre de souverain, that is to say that those persons were ‘exercising functions of state authority there’ on behalf of their national authorities.Footnote 129
Either titles or effectivités may be relied on as having already, before the Court is seised, led to the establishment of an international boundary, which the Court is asked to discern and to declare; but, particularly in the case of effectivités, the role of the Court may, in the contention of one or both parties, be more creative, in the sense that it is asked to apply the recognized law of territorial acquisition by effectivités in order to deduce the existence and position of a boundary.Footnote 130
Changes resulting from effectivités, in boundaries previously established, either by title or by earlier effectivités, may be seen as attributable to consent (tacit or implied). As the Court said in Land, Island and Maritime Frontier Dispute, it is not the case:
that the effect of the application of the principle of the uti possidetis juris . . . was to freeze for all time the provincial boundaries which, with the advent of independence, became the frontiers between the new States. It was obviously open to those States to vary the boundaries between them by agreement,Footnote 131
and found that there had been a modification by acquiescence.
In Land and Maritime Boundary between Cameroon and Nigeria the Court noted that the case before it was one in which ‘the territory which is the subject of the dispute is effectively administered by a State other than the one possessing the legal title’; it concluded that ‘the conduct of Cameroon [the legal title-holder] in that territory has pertinence only for the question of whether it acquiesced in the establishment of a change in treaty title, which cannot be wholly precluded as a possibility in law’.Footnote 132 On the other hand, in the Nicaragua/Costa Rica case the Court stated that ‘[t]he effectivités invoked by the Parties . . . cannot affect the title to sovereignty resulting from the 1858 Treaty and the Cleveland and Alexander Awards’,Footnote 133 the embodiments of the legal title.
As to the relationship between title and effectivités where both are invoked in parallel, in Frontier Dispute (Burkina Faso/Niger) the Court declared that: ‘[w]hile an effectivité may enable an obscure or ambiguous legal title to be interpreted, it cannot contradict the applicable title’,Footnote 134 and that:
[I]t is true, as a general rule, that for the purposes of the uti possidetis principle, the effectivités as established at the critical date may serve to compensate for the absence of a legal title or to complete a defective title . . .Footnote 135
On the other hand, in Pulau Ligitan and Pulau Sipadan, the Court quoted its previous dictum (in Frontier Dispute (Burkina Faso/Mali), that in the event that an effectivité ‘does not co-exist with any legal title, it must invariably be taken into consideration’,Footnote 136 with the implication that any legal title that does exist prevails over the effectivité.Footnote 137
7. Decolonization, independence and the principle of uti possidetis juris
As noted above, it is not always easy to establish just what territory a state possessed, or inherited, or acquired, at the time of independence, and the ICJ has had to deal with numerous cases involving problems of this kind. Since the attaining of independence is not an acquisition but a succession, the question is one of attribution, or its counterpart in the principle of uti possidetis juris, leading to the principle of there being no terra nullius on decolonization.Footnote 138 The Court has found that this doctrine, established in Latin America,Footnote 139 is applicable to all cases of independence on decolonization, in whatever region.Footnote 140 In the Qatar/Bahrain case, Qatar argued that the principle of uti possidetis only operates where there is a succession of states; while this is the legal process in most case of decolonization, it contended that the status of the two sheikhdoms prior to their obtaining full independence was such that there was at that moment no ‘new legal personality’, and no ‘colonial heritage’, and consequently no succession.Footnote 141 The Court, however, found it unnecessary to deal with the point.Footnote 142
The residuary nature of the rule means that if there are two successor states to a single colonial state, and in relation to a particular territory there is no indication which of them inherited, it does not follow that the territory is nullius.Footnote 143 This was the situation in the Territorial and Maritime Dispute between Nicaragua and Honduras,Footnote 144 in which the Court observed that the problem was that while, among the former Spanish possessions, ‘there was no territory without a master’, yet ‘not every single piece of land had a definitive identification or had been attached to a specific administrative authority’.Footnote 145 To claim the disputed islands, Honduras invoked the uti possidetis juris; Nicaragua recognized the principle, but argued that they had never been attributed to one or other of the former Spanish provinces of the Captaincy-General of Guatemala, but appertained directly to the Captaincy-General itself. This would refute the claim of Honduras, while Nicaragua itself claimed them simply on the basis of their proximity to its land territory.Footnote 146 The Court agreed that the question in dispute could not, for lack of information, be settled on the basis of the uti possidetis juris, nor on the basis of colonial effectivités.Footnote 147 It resolved the issue by accepting the argument of Nicaragua that its own activities in the islands were not mere effectivités, but exercise of sovereignty on the basis of an original title, based on adjacency, and thus benefited from the rule that effectivités yield to title.Footnote 148
In Pulau Ligitan, the parties’ predecessors had drawn the boundary line between their possessions by treaty, but disputed whether the terms used meant that the line extended seawards so as to divide off-shore islands. The Court decided that it did not, so that it did not regulate the question of uti possidetis sovereignty over the islands,Footnote 149 and went on to consider and dismiss the possibility that one or the other party had obtained title by succession.Footnote 150 The Court therefore decided the case on the basis of the comparative effectivités;Footnote 151 it is interesting to speculate what might have been the position if a third state had been able to cite effectivités of its own, since at the final stage of the Court's reasoning the parties could no longer rely on their special position as successors.
The physical situation may have changed since the date of independence, in particular as regards maritime features such as islands. In Frontier Dispute (Benin/Niger), the Chamber seised of the case applied the uti possidetis ‘by reference to the physical situation to which French colonial law was applied, as that situation existed at the dates of independence’, but observed that the consequences of doing so ‘must be assessed in relation to present-day physical realities and . . . the Chamber cannot disregard the possible appearance or disappearance of certain islands in the stretch concerned’.Footnote 152
The phrase uti possidetis juris signifies that what passes to the new state is the territory that was in the lawful possession of the pre-existing unit (the colony); and it is colonial law that is the relevant jus, and thus determines where the limits are of the administrative unit that becomes the new state.Footnote 153 Consequently:
the uti possidetis juris principle requires not only that reliance be placed on existing legal titles, but also that account be taken of the manner in which these were interpreted and applied by the competent public authorities of the colonial Power, in particular in the exercise of their law-making power.Footnote 154
The principle assumes that it is the defined colonial administrative unit that becomes independent as a state; it also assumes that the boundaries of the unit are determinable. For this, recourse is to be had in sequence to the following:
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1. Colonial legislative and administrative texts; normally legislative instruments indicating a boundary, but in the Land, Island and Maritime Frontier Dispute the surveyed boundaries of the native Indian settlements (ejidos) were used, because each settlement was allocated to an administrative district;
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2. The practice of the colonial power, referred to as colonial effectivités: what was actually treated as the boundary? Unlike prescription, this is unilateral – it is the demonstration of the intent of the current sovereign. Both these show the extent of the uti possidetis (though in the Caribbean Sea the Court seems to have treated effectivités as a separate issue, perhaps because of the juris element).
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There is also the possibility of conflict between these elements, as in the Frontier Dispute between Benin and Niger, where, faced with conflict between French legislation defining the inter-colonial boundary, and subsequent administrative instruments adopting a different boundary, the Court opted for the later administrative de facto boundary;Footnote 155
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3. Post-colonial effectivités. These may be analyzed in two categories: if a party is (or both parties are) claiming to have, or are treated as having, acquired the disputed territory on independence by succession to the colonial authority, then these activities must be seen as indicating, in the view of the party relying on them, what the colonial boundary had been, or at least what the post-colonial authorities thought it had been. Though post-colonial, they support a colonial assertion of authority. Alternatively, the party concerned may be simply pointing to its effectivités as an exercise of sovereign rights, acquiesced in by the party claiming a title, colonial or otherwise: a post-colonial acquisition through acquiescence, on the basis recognized in Eastern Greenland and the Nicaragua/Honduras case.Footnote 156 The difference is between, on the one hand, relying on colonial inheritance, evidenced by actions in the territory, and, on the other, accepting, explicitly or by implication, that the other claimant had the colonial title, but suggesting that it has effectively renounced it by acquiescence.Footnote 157
8. Boundaries: Straight lines, natural features and rivers
A boundary has legal existence even without being demarcated on the ground; and it is an established boundary even if the instrument defining it contains provision for its variation in certain circumstances.Footnote 158
It was argued by Burkina Faso in the Frontier Dispute with Niger that where a colonial document specified a boundary between two named points, it was to be presumed that a straight line was intended, in the absence of any ‘very particular reason’ to assume the contrary.Footnote 159 The Court did not reject this, but found reasons to conclude otherwise. In Land and Maritime Boundary between Cameroon and Nigeria, the Court indicated straight line boundaries on the basis that this was shown to correspond to the pre-independence boundary between the territories. Costa Rica is claiming straight-lines in two sections of the boundary (‘the shortest line’) in its Application in Land Boundary in the Northern Part of Isla Portillos. Footnote 160
Frequently it is convenient to define a frontier by a natural feature: a mountain chain, a valley, or a river (of which more below). In the past, reference to purely human contributions to the landscape (e.g., villages) have run the risk of becoming obscure with the disappearance of these with the passage of time.Footnote 161
A river, being normally a clear territorial dividing line, is not infrequently selected as an international frontier. Since a river has breadth, and a frontier needs (so far as possible) to be a geometric line (thus having length but no breadthFootnote 162 ), it is of course necessary to determine exactly where the line runs in relation to the waters of the river. It may divide those waters between the riparian states; or it may run along one or other of the banks. Entitlement to any islands in the river may affect the placing of the boundary, or may be deduced as a consequence of that operation, as in the first stage of the Court's findings in Kasikili/Sedudu Island.Footnote 163
If the line does not run along a bank, it is necessary to determine how it relates to the course of the river bed; this is normally done by treaty or other inter-state agreement; and if such an agreement exists, it prevails over any assumptions, or arguments of convenience.Footnote 164 In the Court's decision in Kasikili/Sedudu Island, it was noted that treaties ‘usually refer to the thalweg as the boundary when the river is navigable and to the median line between the two banks when it is not, although it cannot be said that practice has been fully consistent’;Footnote 165 and this was quoted with approval in the decision in Frontier Dispute (Benin/Niger).Footnote 166 In Frontier Dispute (Burkina Faso/Niger), the Court had to interpret pre-independence legislation concerning what had become the frontier between the two states. It found that the endpoint of a particular section of frontier was situated in the River Sirba, or on one of its banks. In determining that that point was in the river, the Court took into account that ‘the requirement concerning access to water resources of all the people living in the riparian villages is better met by a frontier situated in the river than on one bank or the other.’Footnote 167 It then had to decide between the thalweg and the median line, and found that ‘[t]his endpoint is more specifically situated on the median line because, in a non-navigable river with the characteristics of the Sirba, that line best meets the requirements of legal security inherent in the determination of a boundary’,Footnote 168 thus illustrating the inconsistency of practice referred to in Kasikili/Sedudu Island.
A river may rise in one state and, after traversing some of that state's territory, flow into the territory of a neighbouring state. In a case currently pending before the Court, the upstream state in a situation of this kind is claiming that the river in question ‘is not a transboundary watercourse’ and that it is ‘entitled to the use of 100% of its waters’.Footnote 169
9. Across the boundary
As already noted, where an international boundary is constituted by a watercourse, which necessarily has breadth, the principle remains that the boundary is a line, which may be in medio filum, or follow the thalweg, or run along one or the other bank.Footnote 170 In the Frontier Dispute between Benin and Niger, a question therefore arose for which positive international law had as yet given no answer: there were two bridges, each some 300 metres long, across the watercourse which served as the boundary. Niger maintained that:
the construction and maintenance of these structures has been financed by the Parties on an equal basis and that the bridges are their joint property . . . it logically follows that the boundary is situated at the middle point of this joint property and does not follow the boundary line in the river itself.Footnote 171
The Court, however, preferred the solution proposed by Benin, whereby the boundary line on the bridge would follow the course of the boundary in the river, on the ground that:
[t]his solution accords with the general theory that a boundary represents the line of separation between areas of State sovereignty, not only on the earth's surface but also in the subsoil and in the superjacent column of air. Moreover, the solution consisting of the vertical extension of the boundary line on the watercourse avoids the difficulties which could be engendered by having two different boundaries on geometrical planes situated in close proximity to one another.Footnote 172
It is, of course, axiomatic that a state has sovereignty only over its own territory, and can perform acts there which would be unlawful the other side of the boundary, on the territory of another state.Footnote 173 In the case of a river, if the boundary runs along one of the banks, the state on that side of the river has, it seems, no right to draw water from the river. This is implied by the decision in Frontier Dispute (Burkina Faso/Nigeria), cited above, deciding in favour of a boundary in the river (rather than along the bank) so that the riparian population on each side should have access to the water.Footnote 174 Is the situation similar as to navigational rights (where the river is navigable)? In Navigational and Related Rights (Costa Rica v. Nicaragua), there was a claim by one riparian state to rights of navigation in a river whose waters lay entirely within the territory of the other riparian state, either on a treaty basis or as a matter of general law.Footnote 175 Since the Court found it could base its decision on the treaty cited, it held that it was not required to take a position ‘on whether and to what extent there exists, in customary international law, a régime applicable to navigation on “international rivers”, either of universal scope or of a regional nature . . .’.Footnote 176
To carry out works on territory on the other side of an international boundary is clearly a wrongful act. In Certain Activities Carried out by Nicaragua in the Border Area (Costa Rica v. Nicaragua), Nicaragua had constructed caños on Costa Rican territory, and reparation was claimed for these constructions and destruction, in the process, of trees and vegetation; the Court made an award in principle, the terms to be negotiated by the parties.Footnote 177
Nor is it any defence, it seems, that the state acting believed in good faith that it was acting on its own territory; the determination of a territorial dispute involves determining also what past acts were or were not legitimate, on the basis of the law as determined ex post facto. In Certain Activities, in connection with an allegation that Nicaragua had committed unlawful uses of force, the Court observed that ‘[t]he fact that Nicaragua considered that its activities were taking place on its own territory does not exclude the possibility of characterizing them as an unlawful use of force’.Footnote 178
Even in the absence of such activities, and however well sealed an international border against human incursion, some emanations may cross it. In the Pulp Mills case, the Court had occasion to cite the rulings in Corfu Channel and Legality of the Threat or Use of Nuclear Weapons, that it is ‘every State's obligation not to allow knowingly its territory to be used for acts contrary to the rights of other States’,Footnote 179 and added that:
[a] State is thus obliged to use all the means at its disposal in order to avoid activities which take place in its territory, or in any area under its jurisdiction, causing significant damage to the environment of another State.Footnote 180
Nicaragua and Costa Rica were agreed, in their two joined cases decided in 2015, ‘on the existence in general international law of an obligation to notify, and consult with, the potentially affected State in respect of activities which carry a risk of significant transboundary harm’,Footnote 181 and the Court treated this as established. In 2008, Ecuador instituted proceedings before the Court against Colombia, concerning ‘Colombia's aerial spraying of toxic herbicides at locations near, at and across its border with Ecuador’ claiming that ‘the spraying has already caused serious damage to people, to crops, to animals, and to the natural environment on the Ecuadorian side of the frontier, and poses a grave risk of further damage over time’.Footnote 182
In the Pulp Mills case, the claim included a complaint of the noise of the working of the mills; the ‘visual pollution’ of their (presumably unsightly) appearance as viewed from Argentinian territory; and of ‘bad odours’ emanating from the mills and wafting across the boundary, as having a deleterious effect on tourism in Argentina. The Court found that these claims lay outside its jurisdiction, and therefore did not say whether or not such a claim would be legally justified.Footnote 183
In recent years, questions of this kind have been seen, in ICJ decisions as elsewhere, in the context of obligations to protect the environment,Footnote 184 including those on territorial and boundary matters. In the Pulp Mills case, the Court went beyond a claim under a specific treaty provision, imposing an obligation to carry out an environmental impact assessment with respect to activities which may cause transboundary harm, and found that a duty to do this ‘may now be considered a requirement under general international law’,Footnote 185 and this was cited, and followed, in the Nicaragua/Costa Rica case.Footnote 186 Analysis of a state's various procedural and other obligations in this field, as discussed by the Court in these decisions, would, however, take us too far afield.
