A/HRC/44/38 worth elaborating upon. In essence, the question concerns the origin and character of the right to self-defence, which is a narrow exception to the jus cogens prohibition against use of force in international relations. Discerning the implications of State silence in this area is complex, not least because silence can convey vastly different meanings in different circumstances It can signify tacit agreement or imply objection. It may convey an absence of any view at all, or simply a lack of interest. It may also indicate fear or reluctance. 72. The legal starting point is that a norm of jus cogens can be modified only by another jus cogens norm. 133 However, the notion that State silence can modify the content of a peremptory norm, including its auxiliary provisions (such as recognized exceptions to the norms), must be considered with the most extreme caution.134 Claims that State silence may change the content either of the prohibition of the use of force or of the narrow self-defence exception to it, especially claims that purport to widen the grounds for resorting to force, are difficult to defend. 73. The 2018 positions of the International Law Commission do not provide sufficient guidance on these matters. Regarding the potential role of silence in treaty interpretation, the Commission formed the view that “silence on the part of one or more parties may constitute acceptance of the subsequent practice when the circumstances call for some reaction”.135 Yet, the Commission tempered this general notion by emphasizing that “the relevance of silence or inaction for the establishment of an agreement regarding interpretation depends to a large extent on the circumstances of the specific case”.136 74. Regarding acceptance as law (opinio juris) – a constituent element of customary international law with general practice, the Commission concluded that failure to react over time may be evidence of opinio juris provided that States were in a position to react and if the circumstances called for some reaction.137 75. States’ reactions to the position of the Commission reveal a clear absence of consensus. Some have cautioned that their views may be expressed privately rather than publicly, and that their perceived non-reaction or silence may be the result of political and diplomatic considerations, not because they agree with the legal position behind the State act. It is worth noting that jurists have stressed that, when the belief of States is motivated by selfinterest or coercion, it may lack “genuineness” and thus be devoid of legal effect.138 76. Article 51 of the Charter requires Member States to immediately report to the Security Council measures taken purportedly in the exercise of the right of individual or collective self-defence. In the face of an “Article 51 submission” to the Council that invokes an overly broad self-defence claim, is the apparent silence of the Council, its members or other States capable of widening the treaty or customary international law grounds for resorting to force in self-defence? 77. Security Council resolutions and debates may be relevant with respect to the interpretation of the Charter and to the formation, or expression, of opinio juris.139 Moreover, 133 134 135 136 137 138 139 18 that might lead to the erosion of Article 2 (4) of the Charter, which the International Law Commission has determined to be a peremptory norm (jus cogens). www.ejiltalk.org/the-diversity-of-rules-on-the-use-of-force-implications-for-the-evolution-of-the-law. Akande also points to occasions when subsequent practice can legitimately be used to interpret the Charter, such as in relation to the responsibility to protect. Lewis, Modirzadeh and Blum, Quantum of Silence, p. 79. Official Records of the General Assembly, Seventy-third Session, Supplement No. 10 (A/73/10), p. 15. Ibid., p. 80. Ibid., p. 120. Starski, “Silence within the process of normative change and evolution of the prohibition on the use of force”, p. 21. For example, the International Tribunal for the Former Yugoslavia has considered, in its decision of 2 October 1995 in Prosecutor v. Tadić, Security Council resolutions “of great relevance to the formation of opinio juris”. See also www.law.umich.edu/facultyhome/drwcasebook/Documents/ Documents/ILA%20Report%20on%20Formation%20of%20Customary%20International%20Law.pdf and Jessica S. Burniske, Naz K. Modirzadeh and Dustin A. Lewis, Armed Non-State Actors and International Human Rights Law: An Analysis of the Practice of the U.N. Security Council and U.N.