The ICJ’s 2025 Advisory Opinion on Climate Change and the Problem of Attribution
In July 2025, the International Court of Justice (ICJ) issued a landmark advisory opinion in response to the United Nations General Assembly’s request for clarification on states’ obligations and potential legal consequences concerning climate change under international law.[i] In its opinion, the Court concluded that states have binding duties to prevent significant harm to the climate system, including obligations to regulate private actors and to take mitigation and adaptation measures.[ii] Importantly, these duties extend beyond existing treaty commitments, contributing to the crystallization of customary international law.[iii] Yet despite the opinion’s strong legal statements, questions remain about its practical effectiveness, especially given the problem of attribution in climate change litigation.
The ICJ unequivocally recognized climate change as a pressing global issue that gives rise to concrete legal obligations for states.[iv] Rather than limiting its analysis to climate-specific treaties such as the Paris Agreement or the Kyoto Protocol,[v] the Court grounded states’ responsibilities in multiple sources of international law, including customary international law, general principles of environmental protection, human rights, and the law on state responsibility.[vi] Notably, the Court emphasized that a failure to exercise due diligence in preventing climate harm may amount to an internationally wrongful act under the law of state responsibility.[vii] This framing is significant because it highlights states’ responsibility not only for their direct actions, but also for omissions, such as inadequate regulation, continued fossil fuel subsidies, or failures to control private actors operating under their jurisdiction.[viii] Nevertheless, as an advisory opinion, the Court’s conclusions do not carry the legally binding force of a judgment issued in a contentious case.
The central difficulty arises when attempting to link specific climate harms, like sea-level rise, extreme weather events, or cumulative emissions, to the actions or omissions of a particular state in a legally actionable way.[ix] While the ICJ acknowledged that scientific methods increasingly allow for the quantification of each state’s contributions to global emissions,[x] practical attribution remains thorny. Climate harm is cumulative, transboundary, and occurs gradually over time, complicating causation analysis under international law.[xi] Moreover, even if a breach of obligation can be established, there is no clear mechanism within the ICJ framework to compel compliance or enforce remedies following an advisory opinion.[xii]
Despite these limitations, the advisory opinion provides an important legal benchmark and normative standard that can influence future climate governance.[xiii] National courts, international tribunals, and human rights bodies may draw upon the opinion as persuasive authority when interpreting states’ environmental obligations.[xiv] It may also serve as evidence of opinio juris, strengthening arguments that climate-related duties are already embedded in customary international law.[xv] Furthermore, non-governmental organizations, vulnerable states, and civil actors may invoke the opinion in both litigation and advocacy efforts to pressure governments to strengthen climate action and regulatory frameworks.
Ultimately, the ICJ’s 2025 advisory opinion represents a significant development in international law, as it is a clear expansion of international legal principles on climate change. However, its practical impact will depend on whether states, courts, and other legal and political actors are willing to operationalize its reasoning. Persistent attribution issues and the non-binding nature of advisory opinions mean that real change will have to emerge through the opinion’s use in other forums, whether that be domestic courts, treaty bodies, or international political negotiations.
Tori Stanford is a staff member of Fordham International Law Journal Volume XLIX.
[i] See Obligations of States in Respect of Climate Change, Advisory Opinion, 2025 I.C.J. 1 ¶ 1 (July 23, 2025) [hereinafter ICJ Advisory Opinion].
[ii] See id. at ¶ 131–42.
[iii] See id.
[iv] See id. at ¶ 72–73.
[v] The Paris Agreement and the Kyoto Protocol are United Nations climate treaties aimed at reducing greenhouse gas emissions through differing regulatory frameworks. See Jonathan B. Wiener & Tyler Felgenhauer, The Evolving International Climate Change Regime: Mitigation, Adaptation, Reflection, 11 Tex. A&M L. Rev. 451, 459–65 (2024) (discussing the structural and enforcement differences between the Kyoto Protocol and the Paris Agreement).
[vi] See ICJ Advisory Opinion, supra note i, at ¶ 113-73.
[vii] See id. at ¶ 135–39.
[viii] See id. at ¶ 427–28.
[ix] See generally Agnes Chong, The Positive Obligation to Prevent Climate Harm Under the Law of State Responsibility, 34 Geo. Env’t L. Rev. 275, 288 (2022) (noting the limits of applying the law of state responsibility to climate change disputes).
[x] See id. at ¶ 429; See also Sandra Thiam, et al., Weathering the Storm of Global Climate Litigation: Enabling Judges to Make Sense of Science, 54 Geo. J. Int’l L. 563, 575 (2023).
[xi] See Chong, supra note viii.
[xii] See ICJ Advisory Opinion, supra note i, at ¶ 450.
[xiii] See Jeffrey Dunoff et al., International Law, Norms, Actors, Process: A Problem-Oriented Approach 39 (5th ed. 2020).
[xiv] See Jesse Townsend, Medellín Stands Alone: Common Law Nations Do Not Show A Shared Postratification Understanding of the ICJ, 34 Yale J. Int’l L. 463, 482–94 (2009) (analyzing how common law nations utilized ICJ opinions in domestic law).
[xv] See Dunoff et al., supra note xiii, at 64.
This is a student blog post and in no way represents the views of the Fordham International Law Journal.