In 1994, Vaughan Lowe observed that due to the extensive practice of intervention in the affairs of foreign States, ‘[t]he most interesting question regarding the principle of non-intervention in international law is why on earth anyone should suppose that it exists.’ (‘The Principle of Non-Intervention: Use of Force’ in C Warbrick (ed), The United Nations and the Principles of International Law: Essays in Memory of Michael Akehurst (Routledge 1994) 66, 67). Indeed, recent events remain rife with practice that would at first glance appear to constitute interventions in the internal affairs of foreign States, and the language of intervention is often invoked by States in a political manner rather than in a legal sense.
Nonetheless, the International Court of Justice (Court) has recognised that although examples of trespass against the principle are not infrequent, the principle of non-intervention is part and parcel of customary international law (in Military and Paramilitary Activities in and against Nicaragua (Nicaragua v USA) (Nicaragua) [1986] ICJ Rep 3, 202). As a rule of customary international law that remains present in claims before the Court today, in many ways it is remarkable that the principle has not been the subject of more scholarly treatment.
Recent debate over the application of international law to cyberspace has encouraged a proliferation of academic scholarship and an increasing number of statements by States that comment on the status and application of the rule. The author of the book under review, who has expertise in the cyber context and is well-versed in statements by States that have been made in that area, provides a welcome exposition of State practice and relevant sources. Whilst the monograph is structured in a traditional manner, featuring only a final chapter devoted to cyber operations, recent statements by States that have been made in the cyber context are interspersed throughout the text to support its arguments.
The historical introductory chapter is an impressive undertaking that provides perspective to the development of the rule. More recently, and perhaps more relevant to lex lata, the work makes an insightful contribution in examining the travaux préparatoires of the Declaration on Principles of International Law concerning Friendly Relations and Cooperations among States in accordance with the Charter of the United Nations (Friendly Relations Declaration). The author also devotes significant time to two chapters on the interaction of the principle of non-intervention with the right to self-determination, and a further chapter on its interaction with international human rights law and international humanitarian law.
In Nicaragua the Court determined that the non-intervention rule is violated when a State exercises coercion in regard to ‘matters in which each state is permitted, by the principle of State sovereignty, to decide freely’ (Nicaragua, 205). Of these two elements, coercion regulates the line between mere interference—which is not considered to constitute a violation of international law—and a prohibited intervention. In this sense, it ‘defines, and indeed forms the very essence of, prohibited intervention’ (Nicaragua, 205). There is no authoritative source defining coercion in international law, and recent debate has taken place in the cyber context featuring differing views on its nature and scope. The Friendly Relations Declaration, the Helsinki Final Act and Oppenheim’s International Law support a broad understanding of coercion, with the latter stating that ‘interference must be forcible, dictatorial or otherwise coercive in effect depriving the state intervened against of control over the matter in question’ (RY Jennings and A Watts (eds), Oppenheim’s International Law: Volume 1 Peace (9th edn, Longman 1996) 432).
Though what may be ‘otherwise coercive’ is not directly addressed, the author adopts this quotation and argues that coercion can assume two forms, either dictatorial (demands paired with threats) or forcible (exercising power in the territory of another State without its consent or legal justification) (152). A demand is coercive when it is accompanied by a clear, specific and credible threat and the threatened harm is sufficiently serious (153). Dictatorial coercion requires demonstrating intent, whereas intent is presumed in forcible cases (158).
The monograph is not alone in proposing categories of coercion, an approach that is present in a trend of recent literature in the cyber context. A question arises as to the value of proposing such categories in definite terms. There is merit in developing an understanding of coercion if based on State practice and opinio juris. Certain academic works have influenced States in drafting their national positions on the application of international law to cyberspace, including through a process of capacity building. But more general scenarios often discussed by States in the cyber context, such as electoral interference or operations affecting the critical national infrastructure of another State, are subtle, not necessarily entailing demands and threats, and may not be easily captured within the categories set out in the monograph.
The reviewer does not read the monograph as excluding coercion beyond the scope of the proposed categories but this is not necessarily clear from the text. There is reference to a potential category of ‘coercive manipulation’, but the author notes that it remains to be seen whether a ‘sufficiently representative majority of states’ will embrace it (399). Instead, the reviewer understands the approach to reflect that intervention encompasses diverse forms of coercion, extending beyond explicit demands and threats. While categories aid clarity, the core focus appears to remain on identifying conduct that violates the non-intervention principle, which would emphasise the essence of coercion over rigid labels, underscoring its broader applicability.
The Court has shed little light on the content of the rule of non-intervention. The monograph places significant emphasis (146) on the phrasing of a line in Corfu Channel (see paragraph beginning ‘[t]he Court cannot accept such a line of defence …’: Corfu Channel (United Kingdom of Great Britain and Northern Ireland v Albania) (Merits) [1949] ICJ Rep 4, 35), upon which the author relies to suggest that there must be some force involved, though not necessarily armed, that must be manifested to the victim State. However, rather than the Court stating that intervention necessarily involves force, the sentence in question may be understood as merely describing the United Kingdom’s argument.
The fifth chapter of the monograph features an interesting argument that customary international law prohibits third States from assisting any party to an armed conflict by sending armed forces into a civil war in another State, challenging any understanding that intervention with the consent of the territorial State is not contrary to international law. The monograph also draws a distinction between civil strife and civil war which, although qualified, may not always be straightforward in practice (196-97)—though this stems from the ambiguous nature of the law itself rather than from any shortcoming of the work.
The monograph’s depth and thoroughness in collating relevant supporting documents and materials is a great accomplishment. An expansive survey of State practice, much of which has not been presented in prior scholarship, is bolstered by understanding gained from new statements by States made in the cyber context. The work reflects the importance of what States say about the principle of non-intervention in the cyber context, which has significant implications beyond that area of application. This excellent contribution will no doubt serve as the first port of call for any academic or practitioner looking into the subject.
