On 23 July 2025, the International Court of Justice (ICJ) delivered its long-awaited Advisory Opinion on the Obligations of States in respect of Climate Change (for an overview of the opinion, see here). The ICJ identified the erga omnes character of specific obligations pertaining to the protection of the climate for the first time, and its findings regarding the consequences of that character offer a singular opportunity for discussion.
This post first recalls the obligations erga omnes identified by the ICJ, taking into account the positions of the participants in the proceedings on the issue. Second, it discusses the consequences of those obligations in the Advisory Opinion regarding the invocation of responsibility, pointing out the problems of the distinction between injured and “non-injured” States recognized by the Court. Third, the post addresses the effects of the lack of specific consequences regarding breaches of obligations erga omnes in the Advisory Opinion, which could solve a seeming confusion between obligations erga omnes and jus cogens norms in previous cases. Finally, the post offers some thoughts on the ICJ’s lack of an explicit pronouncement on the erga omnes character of human rights obligations.
Obligations erga omnes identified by the ICJ in its 2025 Advisory Opinion
The ICJ addressed the issue of the character of the relevant obligations in a specific section (paras. 439-443) of the Advisory Opinion under an unambiguous title: “Erga omnes character of the underlying obligations”.
The ICJ recalled that a number of participants “maintained that the Court has already found that some obligations implicated by climate change are obligations erga omnes, including most notably, certain international human rights obligations” (para. 439). In the present advisory proceedings, besides recognizing erga omnes character of human rights obligations (as I noted in a previous post), the participants also identified environmental obligations of the same nature.
Several participants considered the obligation to prevent significant harm to the climate system and other parts of the natural environment to have an erga omnes character (Micronesia, WS, para. 125; Ecuador, WS, para. 3.19; Vanuatu, WS, paras. 261-264; DRC, WS, paras. 279-281; Kenya, WS, para. 6.117). Other participants considered that the obligation to cooperate to protect the climate system is owed erga omnes (Kenya, WC, para. 5.25; IUCN, WC, para. 78). More generally, others asserted the erga omnes nature of the obligation to protect and preserve the climate system (Burkina Faso, WS, para. 401; Uruguay WS, para. 86).
The Netherlands held that the obligation to develop, adopt and implement a mitigation policy is an obligation owed towards the international community as a whole (Netherlands, WS, para. 3.49) and that the obligations enshrined in Article 4 of the UNFCCC and Article 4 of the Paris Agreement are applicable erga omnes partes (Netherlands, WS, para. 3.14). Moreover, with a more cautious approach, France invited the ICJ to state whether one or several obligations of the Paris Agreement could be characterized as obligations erga omnes partes (France, WS, para. 208).
In the Advisory Opinion, the ICJ clarified the legal nature of certain environmental obligations. Referring to the commentary to Conclusion 17 of the ILC Conclusions on jus cogens, the ICJ observed “that certain rules of international law relating to global common goods, such as the climate system, may produce erga omnes obligations” (para. 440). It considered “that all States have a common interest in the protection of global environmental commons like the atmosphere and the high seas.” (para. 440). The ICJ’s choice of words is curious, since it did not employ the concept of “global common goods” or “global environmental commons” in any other part of the Advisory Opinion. In its commentary to Conclusion 17, the ILC mentioned “common spaces, in particular common heritage regimes” (para. 3), and not “global common goods”, a concept that perhaps deserved more clarification in the Advisory Opinion.
More important, however, is the ICJ’s conclusion:
“States’ obligations pertaining to the protection of the climate system and other parts of the environment from anthropogenic GHG emissions, in particular the obligation to prevent significant transboundary harm under customary international law, are obligations erga omnes. In the treaty context, the Court recalls that the UNFCCC and Paris Agreement acknowledge that climate change is “a common concern of humankind” (UNFCCC, first preambular paragraph; Paris Agreement, eleventh preambular paragraph), requiring “a global response” (Paris Agreement, Article 2). They seek to protect the essential interest of all States in the safeguarding of the climate system, which benefits the international community as a whole. As such, the Court considers that the obligations of States under these treaties are obligations erga omnes partes” (Para. 440).
The ICJ thus aligned itself with the position expressed by many participants in the proceedings regarding the erga omnes nature of the obligation to prevent significant transboundary harm. However, the reference to obligations “pertaining to the protection of the climate system” lacks precision. Which are those obligations? The ICJ explicitly mentions the obligation to prevent “in particular”, indicating that it is an (important) example, but not the only obligation erga omnes in this context. Indeed, the ICJ included “climate change mitigation obligations” between the obligations owed to the international community (para. 443), and it considered that their conventional counterparts (the “main mitigation obligations set forth in the climate change treaties”) are obligations erga omnes partes (para. 441), a position forwarded by the Netherlands.
One can argue that the duty to co-operate for the protection of the environment also has erga omnes character, as some participants affirmed. Although the ICJ did not explicitly declare so (on its customary value, see Arato and Uriburu), it insisted on the importance of that duty (para. 140) and its links with the (erga omnes) obligation to prevent significant harm to the environment (para. 141).
While this lack of precision in the identification of the obligations having erga omnes character could be criticized, it offers a degree of flexibility for future in concreto assessments. In a complex context (which the ICJ acknowledges in para. 421), that flexibility could be useful in order to interpret the relevant obligations.
The legal consequences of breaches of obligations erga omnes
Invocation of responsibility
The ICJ recalled its previous decisions on obligations erga omnes and erga omnes partes (Barcelona Traction, Belgium v. Senegal and The Gambia v. Myanmar) to observe that those obligations are by their very nature the concern of all States, and that treaties protecting common interests imply, with respect to some provisions, the existence of obligations erga omnes partes. It concluded:
“As a result, all States parties have a legal interest in the protection of the main mitigation obligations set forth in the climate change treaties and may invoke the responsibility of other States for failing to fulfil them” (para. 441).
Indeed, the very essence of obligations erga omnes is the common interest of all States in their fulfilment, and its direct consequence is the invocation of responsibility by all States (or States parties to the treaty establishing obligations erga omnes partes).
Regarding the invocation of responsibility, the ICJ quoted – for the first time in the context of obligations erga omnes – Article 48 ARSIWA (para. 442). It is not a strange reference per se, since Article 48(1)(b) recognizes the right of any State to invoke responsibility in case of breaches of obligations erga omnes, and the ICJ now explicitly recognized the legal standing of all States in relation to them, and not only regarding obligations erga omnes partes, as Paddeu and Jackson stressed. However, this finding has specific deeper implications.
However, I posit that the reference to Article 48 has an adverse effect on the ICJ’s reasoning, since it held:
“There is, however, a difference between the position of injured States or specially affected States on the one hand, and that of non-injured States on the other, as concerns the availability of remedies. While a non-injured State may pursue a claim against a State in breach of a collective obligation, it may not claim reparation for itself. Rather, it may only make a claim for cessation of the wrongful act and assurances and guarantees of non-repetition, as well as for the performance of the obligation of reparation in the interest of the injured State or of the beneficiaries of the obligation breached.” (para. 443)
By giving relevance to Article 48 – and not only to the rule of invocation of responsibility it enshrines – the ICJ accepted the difference – artificial in my view – between injured States and “non-injured States”, a distinction that is hard to explain when it comes to obligations erga omnes. If the obligation is by definition “owed to the international community as a whole”, in case of a breach, it affects the international community as a whole. Therefore, all States are injured in stirpes (i.e., as members of the international community), as authors like Drnas de Clément have rightly pointed out (p. 19). The position of those “specially affected” States could be different in matter of reparation, where the existence of damage is relevant (see commentary to Article 31 ARSIWA), but not for its qualification as the only injured States. The “common interest”, underlying the notion of obligations erga omnes, is not a mere interest, it is a true right to seek compliance with the obligations, since those obligations are owed to all States. Granted, accepting such position can have important implications in the rules governing countermeasures, and the ILC decided to avoid that complex issue in ARSIWA; nonetheless, the distinction remains very hard to understand when global common values (like the protection of the climate system) are at stake.
In The Gambia v. Myanmar, although the respondent had insisted on that difference, the ICJ did not find it necessary to explore the legal significance of terms like “non-injured State” or “specially affected State”. For the ICJ, the main point was the common interest in the fulfilment of the erga omnes partes obligations under the Genocide Convention (paras. 99-100). That reasoning, and the lack of references to Article 48 in the other cases regarding obligations erga omnes (partes) gave the hope of the emergence of a possible trend of blurring the artificial difference between injured and non-injured States, as I have stressed elsewhere (pp. 170-171). I still have hope, but the 2025 Advisory Opinion may be seen as a step against that trend.
Absence of other consequences
Although the ICJ recognized the erga omnes character of the obligations pertaining to the protection of the climate system, it did not assign any particular consequences to their breach, beyond the common consequences for all wrongful acts (cessation, reparation, and guarantees of non-repetition, paras. 444-455). This is curious, because the ICJ usually assigns to breaches of obligations erga omnes, the same consequences provided for in Article 41 ARSIWA for serious breaches of obligations arising from peremptory norms: the duty to cooperation, the duty of non-recognition, and the duty not to render aid or assistance (see the Wall advisory opinion, paras. 159-160; Chagos advisory opinion, para. 180; Occupation of Palestine advisory opinion, paras. 275-279).
With these precedents in mind, several participants in the proceedings also considered that those consequences were applicable to breaches of obligations erga omnes (as mentioned in my previous post).
The confusion between consequences of obligations erga omnes and jus cogens norms was highlighted since its inception in 2004 by Judge Kooijmans (Wall separate opinion, para. 40). However, as the ILC stressed, given the significant overlap between jus cogens and obligations erga omnes, “the deduction that the Court in these decisions was referring to peremptory norms of general international law (jus cogens) is not unwarranted” (ILC, commentary to Conclusion 19 on jus cogens, para. 6).
It is not a coincidence that the former ILC Special Rapporteur on jus cogens, Judge Tladi, drew attention to this issue in his Declaration in these advisory proceedings. After recalling the consequences the ICJ assigned to breaches of obligations erga omnes in the Occupation of Palestine advisory opinion, he warned:
“If we take the 2024 Advisory Opinion at face value, then all breaches of erga omnes obligations, whether those obligations flow from jus cogens norms or not, should attract the consequences of the duty of non-recognition, non-assistance and co-operation. If that is the case, then since the Court in its current Advisory Opinion has identified erga omnes obligations, one would expect that the duties of non-recognition, non-assistance and co-operation would also be identified here as legal consequences resulting from the breach. But the Court does not do so. What’s more the Court offers no reason whatsoever as to why those consequences do not attach to the breaches (of obligations erga omnes) in this case.
In my declaration appended to the 2024 Advisory Opinion, I warned that the Court, by attaching the duties of non-recognition, non-assistance and co-operation to the erga omnes character of obligations was improperly conflating the concepts of obligations erga omnes and jus cogens, and thus opening a can of worms that would create incoherence in the future” (paras. 36-37).
Judge Tladi concludes that the ICJ has come face to face with the incoherence in its jurisprudence, and it chose to pour shade over itself (para. 37).
I think that it is possible to conduct an optimistic reading of this seeming incoherence. Although it could be controversial for some authors, in the Advisory Opinion the ICJ determined – for the very first time – the existence of obligations erga omnes not arising from jus cogens norms. The Court was never clear on the issue, but the past determinations show a notorious overlap between both concepts (self-determination of peoples, basic rules of IHL, prohibition of racial discrimination, etc.). Since in this case arguably there is no such overlap, the ICJ could be seen as implicitly confirming the ILC’s deduction in its commentary to Conclusion 19; in the previous cases, the Court was referring to jus cogens norms, and not only to obligations erga omnes (for a different approach to this issue, see here).
I agree with Judge Tladi that the ICJ should have given reasons for this conclusion, but the optimistic lens I propose dissolves the existence of a new problem.
What happened with human rights obligations?
While the ICJ pronounced itself on the erga omnes character of certain environmental obligations, it remained silent on the erga omnes character of human rights obligations. It is difficult to ascertain the reason for this omission, since the ICJ recognized an important value of human rights obligations in the climate change context (para. 404) and it specifically recalled that a number of participants maintained that the Court has already found that certain international human rights obligations are obligations erga omnes (para. 439). Indeed, a third of the participants held the erga omnes nature of human rights obligations, as I showed in my previous post.
Although the ICJ had no obligation to pronounce on this issue, why did it mention that the participants held that the Court itself had found that certain human rights obligations are erga omnes? Is it implying that it maintains its previous findings without further consideration? One can give an affirmative answer to this last question since “the principles and rules concerning the basic rights of the human person” are at the very core of the concept of obligations erga omnes, as they were coined by the ICJ itself in Barcelona Traction, and the Court did not seem to modify this position. However, a deeper development on this matter by the ICJ could have been useful, mainly to clarify the difference between those human rights obligations that have erga omnes character but do not flow from peremptory norms and those that do flow from jus cogens.
Final remarks
In my previous post, I concluded that the Advisory Opinion presented a great opportunity for the ICJ to clarify issues on obligations erga omnes, their sources and their consequences, and their differences with jus cogens norms. Although the Court did not address directly the erga omnes nature of human rights obligations, as many participants had hoped, the ICJ clarified some of those issues regarding environmental obligations.
First, the ICJ identified environmental obligations with erga omnes character for the very first time: the obligations pertaining to the protection of the climate system and other parts of the environment from anthropogenic greenhouse gasses emissions, including the obligation to prevent significant transboundary harm under customary international law, the climate change mitigation obligations and arguably the duty to co-operate for the protection of the environment.
Second, it is possible to infer from the Advisory Opinion that those obligations do not arise from peremptory norms, thus reaffirming the existence of multiple sources of obligations erga omnes.
Finally, by not assigning to the breaches of these obligations the same consequences for serious breaches of peremptory norms, the ICJ seems to confirm that its previous findings were based on the jus cogens nature of the norms involved, and not on the erga omnes character of the obligations.
There is, however, a cause for concern: the explicit reference to Article 48 ARSIWA and its artificial difference between injured and non-injured states. I insist: in case of a breach of an obligation owed to the international community like the protection of the climate system, all States are injured States, since the obligation is owed to all of them. As I stressed above, the position of the “specially affected” States does not modify this conclusion. I think that the difference between injured and non-injured states presents a problem in order to characterize obligations erga omnes as obligations truly owed to the international community.
Setting this problem aside, the Advisory Opinion has an important value in the legal fight against the serious effects of climate change, and offers an important step in the development of obligations erga omnes in international law.
