On July 23, 2025, the International Court of Justice (ICJ) issued a landmark advisory opinion, holding that nation-states have obligations under international law to mitigate greenhouse gas (GHG) emissions, adapt to the effects of climate change and cooperate in good faith with one another to prevent harm to the climate and environment. If a state fails to meet these duties, the ICJ may conclude it conducted a "wrongful act", and injured states may be entitled to reparations for that wrongful act. Small island nations advocated for the ICJ opinion, which was opposed by major emitting states including the United States (under the Biden administration), China, Saudi Arabia and the European Union (EU). The ICJ opinion introduces a new element to an already complex web of environmental obligations for states, corporations and institutions. While the ICJ advisory opinion is not binding upon state governments, including the United States, it provides persuasive authority to tribunals faced with similar legal questions and provides a backdrop for international customs, which may influence legal obligations. For example, courts in the United States now will need to grapple with U.S. Environmental Protection Agency's (EPA) proposal to revoke the endangerment finding associated with GHG emissions from mobile and stationary sources. Non-governmental organizations, interest groups and other nations may seek to use the legal analysis of the ICJ advisory opinion in future litigation against governments or private companies, though such legal strategies have not garnered much success in United States federal courts.
ICJ Advisory Opinion
In its July 23, 2025, advisory opinion, the ICJ ruled that international law requires states to prevent significant harm to the environment and climate system and to cooperate in good faith to mitigate and adapt to climate change. The case began in 2021 when a coalition of small island nations, led by Vanuatu, sought an advisory opinion from the ICJ on states' climate obligations. In 2023, the court adopted a resolution to consider two questions:
- What are the obligations of states under international law to ensure the protection of the climate system and other parts of the environment from anthropogenic emissions of greenhouse gases for states and for present and future generations?
- What are the legal consequences under these obligations for states where they, by their acts and omissions, have caused significant harm to the climate system and other parts of the environment, with respect to:
-
- States, including, in particular, small island developing states, which due to their geographical circumstances and level of development, are injured or specially affected by or are particularly vulnerable to the adverse effects of climate change?
- Peoples and individuals of the present and future generations affected by the adverse effects of climate change?
Vanuatu argued that climate change poses an existential threat to its nation. It posits that high-emission states are responsible for the rising sea levels and should pay reparations to account for the effects of warming on small island and developing states, as they are "particularly vulnerable" to the effects of climate change while contributing the least to it. Developed and high-emitting countries opposed ICJ adopting the resolution, contending that existing treaties are sufficient to address climate concerns. ICJ disagreed.
The unanimous world court found in favor of the petitioners, holding that states may be held responsible for past and ongoing contributions to climate change and that reparations may be warranted where harm and causation can be established. The ICJ reasoned that multilateral treaties—like the UN Framework Convention on Climate Change (UNFCCC), the Kyoto Protocol and the Paris Agreement, among others—along with customary principles under international law and international human rights law create a "continuing duty" to adopt measures to mitigate GHG emissions and adapt to climate change to protect the environment and human rights. "Developed country parties" (also known as Annex I parties) to the UNFCCC—including the U.S., EU, U.K. and 40 others—have "additional obligations to take the lead in combating climate change." States must cooperate with one another in good faith and "act with due diligence" to implement measures to limit global warming to 1.5 degrees above pre-industrial efforts.
A breach of these obligations "constitutes an internationally wrongful act entailing the responsibility of that state." If states fail to fulfill these duties, "resulting consequences" include ceasing wrongful actions or omissions, guaranteeing non-repetition of wrongful actions or omissions and providing "full reparation to injured states."
A Growing International Trend: Judicially Protected Climate Rights
The ICJ's opinion aligns with a growing body of international legal decisions recognizing climate change as a human rights issue. In May 2025, the Inter-American Court of Human Rights (IACHR) issued its own unanimous advisory opinion, requested by Chile and Colombia, concluding that states must act with "enhanced due diligence" to address the human causes of climate change and protect vulnerable populations. The IACHR emphasized that failure to act may constitute a violation of human rights. Together with the ICJ opinion, these decisions reinforce the idea that climate inaction is a potential violation of international legal obligations with legal consequences.
Contrasts with Deregulatory Agendas
The ICJ opinion comes amidst a backdrop of international deregulatory efforts with respect to climate-related issues. In the United States, the current administration has reversed numerous climate-related policies, including rolling back of the basis to regulate power plant emissions standards, loosening National Ambient Air Quality Standards, proposing to revoke the endangerment finding associated with GHG emissions from mobile sources, and withdrawing the United States from the Paris Agreement. These deregulatory efforts have been joined by Congress invoking the Congressional Review Act to disapprove of California's Clean Air Act waivers.1
Environmental deregulation also has established a foothold in Europe, albeit a less comprehensive one. The EU's recent omnibus directive amended the Corporate Sustainability Reporting Directive (CSRD) and Corporate Sustainability Due Diligence Directive (CSDDD), narrowing the scope of mandatory disclosures and extending implementation timelines, overall weakening the directives, including in relation to climate matters. The EU also has moved to simplify the Carbon Border Adjustment Mechanism (CBAM), a program that puts a price on carbon emitted during the production of carbon intensive goods imported into the EU with the goal of encouraging cleaner industrial production in non-EU countries.2
Implications of the ICJ Advisory Opinion
The ICJ's opinion complicates an already fragmented global framework of environmental and climate-related obligations. Companies, particularly those with significant GHG emissions or involvement in legacy energy industries, should anticipate increased international scrutiny and potential litigation. NGOs, interest groups and other nations may seek to use the legal analysis from the ICJ opinion in potential litigation against corporations or the U.S. government. Plaintiffs may cite the ICJ opinion to argue that states should be liable for failure to regulate private entities' GHG emissions, considering both upstream sourcing emissions and downstream product emissions. The ICJ opinion also may usher in a wave of new arguments using climate science to establish responsibility or invoking environmental justice principles based on disproportionate climate burdens. Historically, EPA's regulation of GHGs under the Clean Air Act (made possible by the endangerment finding) preempted states and private individuals from suing over GHG emissions. However, plaintiffs may be able to litigate GHG emissions without being stymied by federal preemption if EPA revokes the endangerment finding. The ICJ opinion bolsters claims challenging defendants' GHG emissions just as they are newly-available for plaintiffs to make.
However, the ICJ opinion has practical limitations. The ICJ advisory opinion, along with other international advisories, is non-binding and lacks an enforcement mechanism. Additionally, the ICJ opinion does not directly apply to corporations, as its findings are limited to duties of nation-states, not private entities. Though plaintiffs may seek to apply the reasoning from the ICJ opinion to climate-related claims in U.S. courts, they would still need to differentiate their claims from other recent litigation that has been unsuccessful when seeking the same outcome. For example, in one of the most notable climate actions in U.S. federal court, Juliana v. United States, claims that the U.S. government violated the youth plaintiffs' constitutional right to a "climate system capable of sustaining human life" were dismissed by the Ninth Circuit for lack of legal standing. The Juliana court held that it, and other federal courts, are not the proper venue for requests for injunctive relief to "phase out fossil fuel emissions and draw down excess atmospheric CO2. "3 Additionally, the U.S. government, under this or any future administration, is unlikely to use the ICJ decision or its rationale to seek compensation or impose liability on U.S. corporations. As noted above, under the Biden administration, the U.S. opposed the ICJ issuing a broad advisory opinion that would expand state commitments beyond international agreements, and under the current administration, the U.S. has shifted entirely away from adopting or implementing policies relevant to combating climate change, including by announcing plans to retract state and federal government's authority to regulate GHGs, withdrawing from the Paris Agreement for a second time and promoting policies that may increase GHG emissions.
The ICJ's opinion marks a turning point in international climate law. While not binding, it potentially provides a powerful legal foundation and roadmap for future litigation and policymaking. Akin will continue to monitor developments in this space and has advised clients across sectors on navigating climate liability, disclosure and compliance obligations.
Footnotes
1. See our EPA Deregulation Tracker for a list of deregulatory actions.
2. Read more about the proposed CBAM changes and other EU deregulatory efforts here.
3. Juliana v. U.S., 947 F.3d 1159, 1164-65, 1170 (9th Cir. 2020).
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
