The ICJ, Provisional Measures, and the Right of Self-defence: The Unspoken Relevance of jus cogens?

The ICJ, Provisional Measures, and the Right of Self-defence: The Unspoken Relevance of jus cogens?

[Christian Henderson is Professor of International Law at the University of Sussex. He is the author of The Use of Force and International Law (2nd end, CUP, 2023)]


A notable aspect of the International Court of Justice’s decision on provisional measures in the South Africa v Israel case was whether, and if so how, the Court might respond to Israel’s overarching legal justification that it was acting in self-defence, particularly in the face of a request by South Africa that the Court order Israel to ‘immediately suspend its military operations in and against Gaza’. The Court did not make this order, although it did order Russia to suspend its military operations – albeit in somewhat different circumstances – in the provisional measures stage of the Ukraine v Russia case.

A perhaps overlooked element in the discussions regarding these decisions is the potential role that jus cogens norms might have played in the Court arriving at them, or could (or should) play more generally in decisions of this nature.

As noted by the International Law Commission, ‘the Court has been reluctant to pronounce on peremptory norms of general international law (jus cogens)’ (p. 45). And when it has engaged with them it has sometimes been creative in finding ways to avoid their applicability (for example, by separating procedural rules from substantive norms such as in Jurisdictional Immunities of the State (Germany v. Italy: Greece intervening) [para. 92]).

Yet, the Court has previously categorised genocide as ‘assuredly’ a jus cogens norm in Armed Activities on the Territory of the Congo (Democratic Republic of Congo v Rwanda) (para. 64). In addition, while there is some debate as to whether the prohibition of force constitutes a jus cogens norm, or whether this status is reserved for the prohibition of aggression, the Court has offered some support to the unlawful use of force falling within the category of jus cogens: in Military and Paramilitary Activities in and against Nicaragua, Nicaragua v. United States of America (para. 190), the Court observed that the ‘International Law Commission … expressed the view that “the law of the Charter [of the United Nations] concerning the prohibition of the use of force in itself constitutes a conspicuous example of a rule in international law having the character of jus cogens”’. Even this limited engagement demonstrates a commitment to the notion of normative hierarchy and that these norms should prevail over conflicting rights and obligations of states. In light of this, it bears considering the potential role that these jus cogens norms might have played in these decisions of the Court where self-defence has been advanced, and might play in the future should the same issue come before the Court.

South Africa v Israel and the Prohibition of Genocide

in South Africa v Israel the Court seemed to positively disengage from Israel’s claimed right of self-defence, and clearly avoided using the phrase ‘self-defence’ in its order (although for brief references by the Court to Israel’s claim see paras 13, 24, 40, 57). In his Separate Opinion, Judge Nolte implied that this was on jurisdictional grounds; because these cases were brought exclusively under the Genocide Convention it was simply not necessary for the Court to engage issues of self-defence for it to make its decision (para. 5). In other words, any kind of normative clash between Israel’s claimed right of self-defence and its obligations under the prohibition of genocide could, and should, be avoided.

By contrast, it was notable that in Ukraine v Russia, Judge Robinson seemed to put them on a head-on collision, with the right of self-defence taking precedence. Indeed, in his view the right of self-defence ‘cannot be overridden by any pronouncement the Court may make as to the consistency [of a State’s actions] with the Genocide Convention’ (para. 32, emphasis added)). Somewhat echoing this, Lempel has claimed that there was a procedural bar to the Court issuing a suspension of hostilities measure in the face of the justification of self-defence, given that the Court is a creature of the UN Charter and Article 51 clearly stipulates that ‘[n]othing in the present Charter shall impair’ a state’s ‘inherent’ right of self-defence (emphasis added).

Seen in this light, while not necessarily an unqualified endorsement of Israel’s right of self-defence the Court’s decision to refrain from issuing a suspension of hostilities order might be read as it at least recognising that just as there was a plausible claim of genocide, there was also a plausible claim of self-defence which the Court did not feel able to ‘impair’, or at least completely deny.

But, and by contrast, it might be legitimately questioned whether the Court was, on the contrary, under an obligation to issue a suspension of military action in these circumstances. In particular, if the prohibition of genocide is, as proclaimed by the Court itself, a jus cogens norm, should it have been treated as a non-derogable obligation by the Court (Article 53, VCLT (196)), thereby taking precedence over the right of self-defence?

This might be countered with the argument that the inherent right of self-defence is also a ‘norm of general international law having the same character’ (Article 53, VCLT (1969). Yet, while there has been some tentative support for the right of self-defence as jus cogens, this categorisation of the right is from clear, or at least not nearly as clear as that regarding genocide. Alternatively, if not seen as a jus cogens norm, the right of self-defence is nonetheless a circumstance precluding wrongfulness (Art, 21, DARSIWA). Yet, not even an otherwise legitimate claim of self-defence, ‘precludes the wrongfulness of any act of a State which is not in conformity with an obligation arising under a peremptory norm of general international law’ (Art 26, DARISWA).

Genocidal intent is often not clear or the only inference to be drawn from a set of circumstances, of course, as was the case in the provisional measures stage of South Africa v Israel. But what if a state was to make the claim that the only way for it to be able to protect itself – indeed, a central aspect of its claimed defensive necessity – was through the destruction, or partial destruction, of a particular people? Would the Court arguably not only have the right to order a cessation of a military operation and ‘override’ the right of self-defence, but arguably a clear duty to do so? This sort of scenario is difficult to imagine, but not implausible, and admittedly not perhaps a million miles away from some of the statements made by Israeli officials presented to the Court in South Africa v Israel.

Yet, it might be contended that if the purpose of provisional measures is to preserve and protect rights (Article 41, Statute of the ICJ (1945)), and in this case those rights concern the right to be free from genocidal acts, then it can be questioned whether the court was under an obligation to order a suspension of hostilities, even if it was only plausible and not beyond question that there was genocidal intent on the part of Israel and even if the provisional measure has the result of impairing the right of self-defence and be unilaterally imposed upon only one of the belligerent parties.

Ukraine v Russia and the Prohibition of Aggression

In Ukraine v Russia the request for the Court to order an immediate suspension of Russia’s military operations was not to prevent it from committing genocide, but rather to prevent it from using the Genocide Convention as a pretext for its aggressive invasion of Ukraine.

The Court was not as averse to the phrase ‘self-defence’ as it was in South Africa v Israel, and noted on several occasions Russia’s justification of (collective) self-defence under Article 51 of the UN Charter for its ‘special military operation’ (paras 32, 33, 39 and 46).

At play here was not whether the prohibition of genocide ‘overrode’ (to use Judge Robinson’s terminology) the right of self-defence, but rather whether the right of self-defence was overridden by another jus cogens norm, that is, the obligation to refrain from acts of aggression.

As noted above, in South Africa v Israel the evidence regarding the mens rea of genocide, while plausible, was not confirmed, or the only possible inference from the statements of the Israeli officials (something the merits phase will deal with). However, in Ukraine v Russia the Court had at its disposal UN General Assembly Resolution A/RES/ES-11/1, adopted just a few weeks before the decision of the Court of 2 March 2022, expressing the view of 141 states that what Russia was doing constituted aggression (para. 2). While the Court is not expressly obligated to follow such clear determinations of another organ of the UN, it would be unthinkable for it not to follow such a determination, particularly at the provisional measures stage and before it has had the possibility to conduct further investigations.

The Court did refer to this resolution, but not its determination as to aggression, and did not endorse the determination of the UN General Assembly in this respect. Yet, it also avoided the need for the Court to engage in any assessment of Russia’s self-defence claim in making a clear order for the suspension of military operations and there were signs that it was in the minds of the judges in determining whether to grant the order.

In particular, given the Court’s general hesitation to mention or refer to jus cogens norms and issues of relative normativity it was not explicit about this, yet the Court did go as far as to state that it was ‘profoundly concerned about the use of force … which raises very serious issues of international law’ and that it deemed ‘it necessary to emphasize that all States must act in conformity with their obligations under the United Nations Charter and other rules of international law…’ (para. 18).

The Court also made several references to Ukraine’s argument that Russia had used the prevention and punishment of genocide as the pretext for its ‘unlawful aggression’ (paras 42 and 53), and went as far as stating that Ukraine ‘has a right not to suffer grave harm as a result of a military action falsely cloaked as one undertaken to prevent and punish genocide’ (para. 54). What the Court meant by ‘grave harm’ is not entirely clear. But it is certainly possible to read this as referring to a use of force of particular gravity, or in other words an armed attack of act of aggression.

Perhaps most notably, however, Ukraine had been strategically conservative in its request for the Court to order the immediate suspension of military operations ‘that have as their stated purpose and objective the prevention and punishment of a claimed genocide in the Luhansk and Donetsk oblasts of Ukraine’ (para. 5(a)). The Court, however, appeared clearly convinced of the need to suspend Russia’s act of aggression as a whole, and not just those acts that might be perceived as being done with the purpose of preventing genocide and so ordered instead, and more broadly, the immediate suspension of ‘military operations that it commenced on 24 February 2022 in the territory of Ukraine’ (para. 86(1)).


The Court clearly has a difficult role to perform and the need to carefully balance rights and interests. Yet, while it has previously circumvented normative clashes, including those involving jus cogens norms, it does not always acknowledge and tackle these head on when they arise.

In this respect, while it was clear that jus cogens norms were in play in the provisional measures stages of both South Africa v Israel and Ukraine v Russia, the Court – intentionally or otherwise – chose to avoid a normative conflict. Some clarification as to how the right of self-defence relates to state obligations under jus cogens norms particularly in the context of the issuing of provisional measures would have been a welcome addition to the Court’s jurisprudence, particularly given the frequency with which this has been an issue over the last few years.

This was not possible in the preliminary objections phase of the Ukraine v Russia case which was delivered on 2 February 2004. Indeed, the Court in this phase was necessarily restricted to the jurisdictional grounds upon which the Court could proceed to the merits phase of the case. However, and of significance, the Court was keen to stress that despite these jurisdictional limitations ‘states are always required to fulfil their obligations under the Charter of the United Nations and other rules of international law’ (para. 150).

With the report recently submitted by Israel to the Court on the measures taken by it to give effect to the Court’s order on provisional measures, it awaits to be seen how this will be treated and responded to by Court, if at all. In particular, the Court has previously ramped up its provisional measures in light of such reports (indeed, it did so five times within two years in Application of the International Convention on the Elimination of All Forms of Racial Discrimination (Armenia v. Azerbaijan)), so depending upon events and the substance of the report it is not completely off the cards that the Court will yet engage more directly with the right of self-defence and how it relates to the jus cogens norm at play. In this sense, while unlikely, it may still yet order a suspension of military operations.

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