Business and Human Rights: ICJ issues opinion on State obligations in respect of climate change

On 23 July 2025, the International Court of Justice (ICJ) issued a landmark advisory opinion at the request of the United Nations General Assembly, holding that States have a legal obligation to protect the environment, including to address climate change (the “Opinion“). The Opinion also recognised that a “clean, healthy and sustainable environment” is a human right and sets out the consequences for a State’s breach of its legal obligations. Although not legally binding, the Opinion is likely to influence the policy choices of governments and businesses alike, future treaty negotiations and domestic and international litigation.

Background

The origins of the Opinion can be traced to a grassroots initiative launched in March 2019 by the Pacific Islands Students Fighting Climate Change, a collective of Vanuatu-based university students who petitioned every Pacific government to seek an advisory opinion from the ICJ. That effort culminated on 29 March 2023 with the adoption of UN General Assembly Resolution 77/276, which formally requested the advisory opinion. This marked the first time that the UN General Assembly had referred a legal question to the ICJ by consensus, demonstrating overwhelming interest in receiving clarification on the obligations of the State with respect to the climate.

The Opinion is one of three recently published advisory opinions that outline States’ obligations with respect to climate action, the others being:

• The Inter-American Court of Human Rights (IACHR) issued an advisory opinion on 3 July 2025 clarifying States’ human rights obligations in the face of climate change. Among other things, the IACHR held that an independent right to a healthy climate exists, separate to but derived from the right to a healthy environment.
• The International Tribunal on the Law of the Sea also issued an advisory opinion last year on States’ obligations under the UN Convention on the Law of the Sea. It found that greenhouse gas emissions absorbed by the oceans constitute marine pollution and that States must take all necessary measures to prevent, reduce, and control such pollution.

These advisory opinions in turn follow developments at the UN General Assembly – in July 2022 the UN General Assembly resolved to recognise the right to a “clean, healthy and sustainable environment”. Further, the intersectionality between human rights and environmental protections is explicitly recognised in the Corporate Sustainability Due Diligence Directive (see here for further Mayer Brown insight on CSDDD).

States’ Key Legal Obligations

The Opinion clarifies the legal duties of States under treaties, customary international law, and human rights law and outlines the legal consequences of acts or omissions that cause significant harm to the climate and environment.

The ICJ found that States must implement measures to cut greenhouse gas emissions and adapt to the impacts of climate change. Adaptation measures must evolve with scientific knowledge. All nations are required to work together, exchanging technology, financial support, and information to achieve these goals.  Developed nations, in particular, are expected to lead mitigation efforts and assist developing and vulnerable countries in adapting to climate impacts.  The Court also clarified that Nationally Determined Contributions (NDCs) – the climate action commitments under the Paris Agreement – are binding obligations of conduct and that not preparing, updating, or maintaining NDCs is considered a breach of international law.  These NDCs must be ambitious enough to contribute to the global target of limiting temperature rise to 1.5°C.

The ICJ further stated that countries not party to climate treaties are still obligated under customary international law to protect the environment and address climate change.  The Court also affirmed that the right to a clean, healthy, and sustainable environment is recognised as a human right.

Legal Consequences of Breach

The ICJ confirmed that a breach by a State of any of the identified obligations constitutes an internationally wrongful act, triggering the following legal consequences:

• Duty of Performance: The State must perform their international obligations despite breaches thereof.
• Cessation and Non-Repetition: The State must cease the wrongful conduct and provide assurances against recurrence.
• Reparation: The State must make reparation for the damage caused, which may include restitution, compensation, and satisfaction.

Potential Implications

Although the Opinion is not legally binding and only deals with States’ obligations, the Opinion raises the legal stakes for inadequate climate action and may have significant implications for businesses:

• Stricter Regulation: By clarifying and reinforcing States’ obligations to prevent significant harm to the climate and to regulate greenhouse gas emissions, the Opinion is likely to drive more stringent national legislation and regulatory measures affecting business operations.  Businesses should prepare for more rigorous climate-related laws and closer oversight of their environmental performance.
• Heightened Due Diligence: States are required to exercise due diligence in regulating private actors, meaning businesses can expect increased scrutiny of their emissions, supply chains, and environmental practices. Businesses operating in sectors with high greenhouse gas emissions, such as energy, transportation, agriculture, and manufacturing, may face tighter reporting requirements and intensified due diligence obligations across the value chain.
• Litigation Risk: The Opinion increases the risk of legal action between States and also against businesses for their impact on the environment. The opinion may give claimants stronger grounds to sue businesses whose actions cause or contribute to climate harm, which could lead to more and stronger lawsuits seeking emission cuts or compensation for damages.
• Greater Transparency: The various international law frameworks used to protect the climate and address climate change place importance on openness and accountability. Businesses may be required to provide more detailed reporting on their emissions and climate risks.
• Support and Opportunity: Developed nations are mandated to offer financial and technological assistance to help developing countries mitigate and adapt to climate change. This creates both obligations and potential new markets for financial services, technology firms, and global businesses.
• Human Rights Integration: There is growing recognition of the link between climate action and human rights. Businesses should be mindful of the risk of climate-related human rights claims and ensure they respect the rights of impacted communities, including indigenous peoples and other vulnerable groups.

Overall, businesses should prepare for more rigorous climate-related laws, closer oversight of their impact on the environment and increased litigation risk. The Opinion may turn what many businesses see as policy choices into clear legal obligations.

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