The Nature of States’ Obligations in Respect of Climate Change and the Applicability of the Law of State Responsibility : A Critical Review of the 2025 ICJ’s Advisory Opinion on Obligations of States in respect of Climate Change

Abstract

Through its 2025 Advisory Opinion on the Obligations of States in Respect of Climate Change, the ICJ indicated that the standards for the States’ obligations under international law concerning climate change are becoming stringent and that a breach of such obligations may entail all the legal consequences arising from State responsibility. However, the fact that the standards for the performance of these obligations have become more stringent does not, in itself, ensure the applicability of the law of State responsibility to their implementation. In this respect, a logical gap can be identified in the Court’s Advisory Opinion. Against this background, this article critically examines the applicability of the law of State responsibility to climate change-related obligations, based on an understanding of the nature of those obligations. According to the ICJ, States’ obligations relating to climate change may be divided into substantive and procedural obligations. The former are obligations of conduct, compliance with which is assessed primarily on the basis of due diligence. Given the variable nature of the due diligence standard, as well as the temporal dimensions of climate change and the applicable law, establishing a breach of such obligations may prove difficult. Moreover, where a breach consists of an omission, establishing a causal link between the omission and the resulting damage at the stage of compensation may also present significant difficulties. Procedural obligations, by contrast, are obligations of result, and their breach may be relatively easier to establish. Nevertheless, difficulties may arise in demonstrating the existence of damage, as well as a causal link between such damage and the breach, both of which are necessary to the award of compensation. Furthermore, where the invocation of State responsibility is at issue, caution should be exercised against placing excessive emphasis on the role of scientific knowledge. Although advances in science may make it increasingly possible to establish a causal link between greenhouse gas emissions and environmental harm, the questions ultimately to be determined under the law of State responsibility remain matters of legal judgment that cannot be resolved solely on the basis of scientific information. Moreover, a State responsibility-centered approach is not only uncertain in terms of its practical applicability but also inappropriate given its limited scope in material, personal, and temporal terms. The questions submitted to the Court for its Advisory Opinion can be understood to have been strategically formulated to reflect the underlying orientation of international environmental law. The first question asked what the obligations of States are, while the second did not simply ask about the “responsibility” arising from a “breach” of those obligations, but instead addressed the legal consequences where “significant harm” occurs in relation to such obligations. This formulation suggests that climate change-related harm should be addressed from broader material, personal, and temporal perspectives than those offered by the law of State responsibility. The logical gap between the Court’s answers to the first and second questions reveals the need for a community-oriented approach to climate change and the raison d’etre of the climate change treaty regime.