The ICJ’s advisory opinion delivered on 23 July 2025 and relating to obligations of States in respect of climate change generated numerous enthusiastic reactions, both in the media and among academic commentators or NGOs. It has been described as a landmark decision, a turning point for climate justice, and a historic win for small island States. While there are many reasons to welcome this advisory opinion, particularly for its contribution to the clarification of international environmental law and for the international legal order as a whole, it is important not to be overly optimistic.
Firstly because, as pointed out by the Court, its contribution in this area could only be limited. The issue of climate change attracts considerable attention, and is “an existential problem of planetary proportions” that cannot be reduced to its legal implications. The Court emphasized its important but limited role in a debate that can only find a satisfactory solution through “human will and wisdom” (Advisory Opinion, para. 456).
Secondly because, in some respects, the Court’s responses appear disappointing or do not measure up to the challenges. The request for an advisory opinion was submitted by the UN General Assembly to the ICJ through a resolution which highlighted the particular situation of small islands and developing countries and emphasized their vulnerability to the adverse effects of climate change. More specifically, the second question in the advisory opinion draws a clear distinction between two categories of States. On the one hand, States that through “their acts or omissions have caused significant harm to the climate system”, and on the other, those that due to “their geographical circumstances and level of development, are specially affected by, or particularly vulnerable to the adverse effects of climate change”. The question put to the Court sought to determine the legal consequences, in the event of a breach of their obligations by States from the first group, with respect to the States from the second group. Yet the Court only addresses this issue superficially and ignores the idea of climate justice that was at the very heart of the request.
Thus, although it distinguishes between developed and developing States when determining the obligations incumbent upon States, it adopts a restrictive interpretation when determining the legal consequences of violations of such obligations with respect to particular injured States. As a result, little consideration is given to the vulnerability of States, particularly small island developing States.
Distinguishing Between ‘Developed’ and ‘Developing’ States
Among the many positive aspects of the opinion is the fact that the Court clarifies key aspects of States’ legal obligations in respect of climate change. When doing so, the Court refers to several treaties that distinguish between ‘developed’ and ‘developing’ countries, such as the UNFCCC, the Kyoto Protocol or the Paris Agreement. This distinction is also to be found at heart of the principle of common but differentiated responsibilities and respective capabilities, that the Court considers to be a cardinal principle of the climate change treaty framework, and a “core guiding principle” for the interpretation of the provisions of said treaties. It also establishes a link between this principle and the determination of the applicable standard of due diligence, by considering that the latter depends on each States’ capacities. Even though the obligation of due diligence requires all States to take all the means at their disposal to protect the climate system, the Court emphasizes the fact that “developed States […] must take more demanding measures to prevent environmental harm and must satisfy a more demanding standard of conduct” (para. 292). In addition, it emphasises the fact that the categorisation of States as “developed” or “developing” is not static and also recognises the evolving nature of the due diligence standard.
While it is to be welcomed that the Court acknowledges the distinction between the major emitting states and the vulnerable states that have contributed least to climate change, its approach nevertheless suffers from certain limitations. First of all, although the principle of common but differentiated responsibilities is recognized as a structuring principle, one may regret the fact that the Court is only using it as an interpretative framework, without considering it to be an autonomous rule with an identified normative content. Second, while establishing a clear distinction between ‘developed’ and ‘developing’ States in terms of GHG emissions, the Court fails to give full historical dimension to its reasoning. It underlines that among the States that are in the middle of the spectrum, some have made considerable progress in terms of development over the last few decades, and “now contribute significantly to global GHG emissions” (para. 150). However, as pointed out by Judge Yusuf in his separate opinion, this statement neglects the fact that “historical emissions of industrialized countries continue to have a significant impact on the current climate system” (Yusuf, para. 13). By refusing to draw conclusions from this, the Court waters down the principle and deprives the most vulnerable States of the enhanced legal protection that it should have offered them.
Avoiding Question b) Through Restrictive Interpretation
The UN General Assembly had requested the Court to determine the legal consequences, in the event of a breach of their obligations for States that have adversely affected the climate system, with respect to States that are ‘specially affected’ or ‘particularly vulnerable’ such as the least developed countries and small island developing States. However, at the outset of the advisory opinion, the Court interprets the scope of the question referred to it and begins by stating that “it is not called upon to determine the responsibility of any group of States under international law” (para. 106), presumably out of concern for not lapsing into “finger pointing”.
Of course, the Court was here constrained by the fact that it was seized in its advisory jurisdiction, which is arguably not designed to determine whether the activities of a particular State or group of States are in accordance with international law and trigger its responsibility. Nevertheless, one may be surprised by such elliptical reasoning. Even if the Court was not called upon to provide for an individual assessment of any State’s conduct, it was clearly asked to clarify the legal consequences for the breaches of its obligations by one group of States, towards another group of States.
Instead, it eludes the question that is asked and simply acknowledges that certain States are likely to face greater levels of climate change related harm, due to the acts or omissions of other States, without drawing any specific legal consequences thereon. To the contrary, it merely declares that States that are ‘particularly affected’ or ‘particularly vulnerable’ “are in principle entitled to the same reparation as any other injured State” (para. 109). It is regrettable that the recognition of an asymmetry between major polluters and vulnerable states has not found any echo in the determination of applicable secondary rules.
On the whole, the Court’s findings on responsibility are limited to generalities. For example, the developments relating to reparation are very concise, where the Court could have elaborated further to explain how this applies to the specific context of climate change, and could have specified that appropriate reparation may include such remedies as money compensation, or reforestation (Sebutinde, para. 12).
Gaps in Addressing Climate Change’s Impacts on Vulnerable States
Finally, its conclusions regarding some of the arguments put forward by the most vulnerable states concerning the protection of climate refugees, the preservation of maritime entitlements, or the continuity of statehood in the face of rising sea-levels are also subject to criticism. While they may seem satisfactory at first glance, the Court’s laconism on these matters makes them particularly nebulous. This is particularly the case with regard to the Court’s assertion that “once a State is established, the disappearance of one of its constituent elements would not necessarily entail the loss of its statehood” (para. 363). The Court thus rules on a matter of particular importance, but since it does not elaborate further on this issue, this dicta resembles a “Delphic pronouncement” (Tomka, para. 11). Moreover, one might wonder whether, by remaining so evasive, it can truly respond to the fears of the most vulnerable States, who fear the submersion of their territories.
Similarly, the Court’s conclusion is also particularly brief when mentioning the fact that sea-level rise may lead some individuals to seek refuge in another country. Although it recognizes the principle of non-refoulement in the context of climate-induced displacement, the fact that only one single paragraph to this issue shows that it only attracted little attention from the Court.
The Court’s circumventions and laconism in response to the second question contained in the request for an advisory opinion are regrettable, but perhaps unavoidable. It was certainly not easy for the Court to engage more fully without exposing itself to severe criticism from States. It also probably needed to remain somewhat evasive in order to preserve unanimity among the judges. Nevertheless, this strategy also has its drawbacks. As outlined by Judge Tomka, “the Court is enhanced not by mystique but by reasoned analysis” (Tomka, para. 11).
Conclusion
The advisory opinion is to be welcomed as it comes at a time when international law is facing constant questioning, and when the climate change issue constitutes an enormous challenge and appears more urgent than ever. In addition to the clarifications it provides, the opinion is an important confirmation that the well-established rules of State responsibility apply to climate change. In this respect, it undoubtedly carries a heavy symbolic weight. However, it should not be treated as groundbreaking, as the Court could probably have drawn more conclusions from the fact that climate change is undeniably haunted by profound inequalities. As such, it tends to leave – as is often the case – the issue of climate justice in the shade.
