HIGHLIGHTS

ICJ Issues Landmark Advisory Opinion on State Obligations for Climate Change 

Background

The International Court of Justice (ICJ) has delivered its long-awaited Advisory Opinion on the Obligations of States in Respect of Climate Change, providing the most comprehensive judicial interpretation of international legal obligations relating to climate change. The opinion was requested by the United Nations General Assembly (UNGA) following a global campaign initiated by students from the University of the South Pacific and supported by Vanuatu and other climate-vulnerable nations.

The request arose from growing concerns that existing international climate commitments lacked clear legal accountability. While the Paris Agreement (2015) requires States to submit Nationally Determined Contributions (NDCs) to reduce greenhouse gas emissions, its implementation largely depends on national commitments rather than enforceable international sanctions. The ICJ was therefore asked to clarify the legal duties of States under international law concerning climate protection.

Current Development

In its Advisory Opinion, the ICJ held that States have binding obligations under international law to protect the climate system from the harmful effects of greenhouse gas emissions.

The Court concluded that States must take appropriate measures to prevent significant environmental harm, implement effective climate policies, and cooperate internationally to address climate change. It further recognised that failure to take adequate action to reduce greenhouse gas emissions may constitute an internationally wrongful act where a State breaches its legal obligations.

The Court also emphasised that States must exercise due diligence in regulating private actors operating within their jurisdiction whose activities contribute significantly to climate change. Although the opinion is advisory and not legally binding, it carries considerable legal authority and is expected to influence international and domestic courts worldwide. 

Legal Analysis

The ICJ based its reasoning on several sources of international law, including the United Nations Framework Convention on Climate Change (UNFCCC), the Paris Agreement, customary international law, and general principles governing State responsibility.

The Court reaffirmed the customary international law principle of sic utere tuo ut alienum non laedas, requiring States to ensure that activities within their territory do not cause significant environmental harm to other States or areas beyond national jurisdiction.

The judges also stressed the importance of due diligence, holding that States must adopt appropriate legislative, administrative, and regulatory measures to reduce emissions and supervise private industries whose activities significantly affect the climate.

Importantly, the Court linked climate protection with international human rights law, recognising that climate change threatens fundamental rights, including the rights to life, health, food, housing, and self-determination. The opinion further acknowledged that States owe responsibilities not only to present populations but also to future generations, reinforcing the principle of intergenerational equity.

Why the Opinion Matters

The Advisory Opinion represents one of the most significant developments in international environmental law.

First, it confirms that climate protection is grounded in existing legal obligations rather than being solely a matter of political commitment or voluntary policy.

Second, the opinion strengthens the principle of State responsibility by clarifying that inadequate climate action may give rise to international legal consequences where treaty or customary law obligations are breached.

Third, the ruling is expected to influence future climate litigation before national, regional, and international courts by providing authoritative guidance on States' legal responsibilities.

The opinion is also likely to encourage governments to strengthen domestic climate legislation, regulate major greenhouse gas emitters more effectively, and align national climate policies with international legal standards.

Conclusion

The ICJ's Advisory Opinion marks a historic milestone in the development of international climate law. By recognising that States have binding obligations to protect the climate system and prevent significant environmental harm, the Court has strengthened the legal framework governing global climate action.

Although advisory opinions are not legally binding, this decision is expected to shape future climate litigation, influence international negotiations, and guide domestic courts in interpreting environmental obligations. It is likely to remain a landmark authority on State responsibility and climate governance for years to come. 

References

International Court of Justice, Advisory Opinion on the Obligations of States in Respect of Climate Change (23 July 2025).

United Nations Framework Convention on Climate Change (UNFCCC).

Paris Agreement (2015).

United Nations General Assembly Resolution A/RES/77/276.

Vienna Convention on the Law of Treaties (1969).

United Nations News.

Reuters.

BBC News.

The Guardian.

Climate Home News.

International Institute for Sustainable Development (IISD).

UN Environment Programme (UNEP).