International court advisory opinions on climate obligations seek new era of legal accountability

The International Court of Justice (ICJ) recently delivered a landmark advisory opinion clarifying the legal obligations of States under international law to address climate change. The opinion was published on July 23, 2025, mere weeks after the Inter-American Court of Human Rights (IACtHR) issued its own advisory opinion on the intersection of climate change and human rights, with a focus on the protection of vulnerable groups and climate-induced displacement.

Together, these opinions mark a significant evolution in the international legal landscape, reinforcing the binding nature of climate obligations for States – and, by extension, the private sector – and signaling what activists hope to be a new era of accountability for the effects of climate change.

The role of international courts and advisory opinions

The ICJ and IACtHR are among the most authoritative international judicial bodies. The ICJ, as the principal judicial body of the United Nations (UN), issues advisory opinions at the request of UN branches or agencies to clarify points of international law. Although not legally binding, the Court’s advisory opinions carry substantial legal and moral authority, often shaping the development of international and domestic law, treaty interpretation, and State conduct. The IACtHR, the highest human rights court in the Americas, is responsible for interpreting the American Convention on Human Rights and related treaties. It was created through the Organization of American States (OAS) with the capacity to issue binding opinions on OAS Member States [1] that have accepted its jurisdiction. While the IACtHR can issue binding rulings in matters involving human rights violations, it can also issue advisory opinions when the OAS or its bodies seek them in relation to consistency of international laws or practices with the American Convention on Human Rights and the interpretation of the Convention or other human rights treaties applicable in the Americas.

Advisory opinions are not judgments in contentious cases but serve to clarify legal standards and shape international expectations, and they are frequently cited in litigation and policy debates. Their influence extends to treaty negotiations, domestic legislation, and judicial decisions, and they often serve as persuasive authority in both international and national courts. The recent opinions from both courts will reshape the legal discourse on climate change, human rights, and the responsibilities of both States and private actors.

Key findings of the ICJ advisory opinion

The ICJ’s landmark advisory opinion on the Obligations of States in Respect of Climate Change was issued in response to a request from the United Nations General Assembly following a campaign led by Vanuatu and a coalition of other small island States. The General Assembly asked the Court what legal obligations States have under international law to protect the climate system from greenhouse gas (GHG) emissions and the legal consequences for States whose acts or omissions cause significant harm to the climate system and environment.

The Court defined the “climate system” as the global system consisting of five major components: the atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere, and the interactions between them in line with the Intergovernmental Panel on Climate Change (IPCC) definition. This is also consistent with the definition in Article 1, paragraph 3, of the UN Framework Convention on Climate Change (UNFCCC), reflecting a comprehensive and integrated view of the earth’s systems. The Court stated that it would rely primarily on the IPCC reports, which it recognized as constituting the best available science on the causes, nature, and consequences of climate change.

The ICJ concluded that all States, regardless of their participation in specific treaties, have binding legal obligations under both treaty law and customary international law to ensure the protection of the climate system and other parts of the environment from anthropogenic (human-caused) GHG emissions. The proceedings involved more State participants than any prior advisory opinion, and it made history as the first unanimous advisory opinion the ICJ has ever issued.

• Treaty obligations. State parties to climate treaties must:


• Adopt measures to mitigate GHG emissions and adapt to climate change


• Cooperate internationally to achieve climate objectives


• Prepare, communicate, and maintain progressive nationally determined contributions (NDCs) under the Paris Agreement, aiming to limit global warming to 1.5°C


• Pursue domestic mitigation measures and fulfill adaptation and cooperation obligations, including technology and financial transfers


• Customary international law. All States, regardless of treaty participation, must:


• Prevent significant harm to the environment by acting with due diligence.


• Cooperate in good faith through sustained and continuous efforts to prevent environmental harm.

In addition, States must take necessary measures to protect the climate system as part of their obligation to ensure the effective enjoyment of human rights, including the right to a clean, healthy, and sustainable environment.

Importantly, the Court stated that the obligations to protect the climate system are considered erga omnes, meaning States owe them to the international community as a whole. Thus, any State may invoke responsibility for breaches. A breach of these obligations constitutes an internationally wrongful act, triggering State responsibility. Legal consequences include the duty to cease wrongful conduct; guarantees of non-repetition; and full reparation, which may take the form of restitution, compensation, or satisfaction. The Court rejected the “drop in the ocean” defense, affirming that even small contributions to global emissions can give rise to legal responsibility.

Key findings of the IACtHR opinion

On July 3, 2025, IACtHR issued a landmark advisory opinion on the Climate Emergency and Human Rights (AO–32/25 or Opinion) in response to requests by the Republic of Chile and the Republic of Colombia.

The IACtHR’s advisory opinion framed the climate emergency as a human rights issue, interpreting States’ obligations to address climate change impacts through the lens of the American Convention on Human Rights. The Court explicitly recognizes the existence of a peremptory jus cogens norm – ie, one that permits no derogation – prohibiting anthropogenic conduct that could irreversibly harm the interdependence and vital equilibrium of the common ecosystem that makes life possible for all species.

The Court highlighted that climate change is driven by GHG emissions from human activities, especially since the industrial revolution, with fossil fuel combustion as the main source.

The IACtHR held that States have general obligations to ensure, respect, guarantee, and progressively realize human rights in the context of climate change. These obligations include:

• Enhanced due diligence: States must proactively identify risks, adopt ambitious preventive measures, use the best available science, and integrate human rights into climate policies.


• Adoption of domestic legislation: States must incorporate necessary regulations to ensure these rights.


• Cooperation: States must cooperate internationally – especially to support developing countries – through financial, technical, and scientific means.

The Court’s advisory opinion held that States are required to promptly develop and regularly update national adaptation plans and targets to protect human rights affected by climate change, with the planning process being immediately enforceable, while the full implementation of these plans is to be progressively realized over time.

Most importantly, the Court held that business enterprises play a crucial role in addressing climate change and that States are obliged to regulate the conduct of business enterprises to ensure compliance with human rights obligations. This includes:

• Urging all business enterprises within their jurisdiction to take effective measures to combat climate change and its impacts on human rights


• Enacting legislation that requires businesses to conduct human rights and environmental due diligence across their entire value chain, specifically addressing climate-related impacts


• Requiring public and private businesses to disclose GHG emissions throughout their value chain in an accessible manner and take concrete steps to reduce emissions and contribute to national and international climate mitigation targets


• Implementing regulations to prevent greenwashing and undue corporate influence in policymaking, and to support human rights defenders

According to AO–32/25, States must also ensure that business enterprises establish and implement effective due diligence processes tailored to their size, sector, and operating context. These processes should cover all operations, products, and services, including domestic and international supply chains.

The Court’s interpretation applies to all OAS Member States who are parties to the Court, reinforcing the interdependence of human rights and environmental protection and providing a legal framework for addressing climate change within the Inter-American human rights system.

The ICJ and IACtHR opinions converge on several key points. Both recognize that climate change is not only an environmental issue but a human rights challenge. They emphasize the binding nature of States’ obligations to prevent significant harm, act with due diligence, and cooperate internationally. Both courts highlight the necessity of integrating human rights considerations into climate action, particularly for vulnerable and marginalized groups.

The opinions also reinforce that States must regulate private actors, including corporations, to ensure their activities do not contribute to climate harm. Both courts stress that legal responsibility is not negated by the collective or cumulative nature of climate change, meaning even small contributions to global emissions or harm can trigger accountability.

What US companies need to know

Advisory opinions are nonbinding. They cannot be directly enforced, and they create no private right of action. But they could influence national regulatory efforts, judicial reasoning, and stakeholder expectations globally.

The practical effects will unfold incrementally through legislation, enforcement, and litigation strategies in the following ways:

First, companies operating in OAS member countries should anticipate increasing regulatory activity, particularly those who accepted the court jurisdiction. Countries who have not accepted the court jurisdiction, such as Canada, may still use the court decision as inspiration for regulatory change. Notwithstanding the United States’ present position on removing itself from the Paris Agreement, US and Canadian companies with cross-border operations or supply chains in the OAS region might still be impacted and the opinion may carry significant strategic and legal implications.

Second, both advisory opinions may serve as persuasive authority in litigation, particularly in jurisdictions where courts engage actively with international law. Non-governmental organizations (NGOs), investors, and affected communities may be able to rely on the opinions to support legal claims asserting that corporate activities contribute to adverse climate and human rights outcomes.

Third, these opinions reinforce the emerging global norm that climate change is a human rights issue. The IACtHR’s recognition of a peremptory norm prohibiting irreversible environmental harm and the ICJ’s classification of climate obligations as one owed generally to the international community elevate the legal and moral imperative for both States and private actors to act. While these classifications do not automatically translate into domestic liability exposure for US businesses, they indicate the trajectory of international legal standards that may be particularly acute for multinational companies.

Questions have arisen as to the implications on this decision for non-members to the treaty, in light of the United States’ recent withdrawal from the Paris Agreement in January 2025. While the US withdrawal will take effect in January of 2026, the ICJ advisory opinion directly addresses that international climate obligations do not depend solely on treaty participation, emphasizing that certain duties (including concerning climate protection) bind all States regardless of treaty status and are thus owed to the international community as a whole. Thus, even outside the Paris framework, the Court held that States remain bound by core climate-related duties under general international law. This may also mean that withdrawal from the Paris Agreement will not inherently shield US companies from evolving global norms or the legal and reputational risks associated with non-alignment, especially when operating in other countries.

Learn more about the implications of these opinions by contacting any of the authors or your DLA Piper relationship lawyer, and please visit our Sustainability and Environmental, Social, and Governance (ESG) portal for the latest information on ESG developments.