The ICJ’s climate ruling: Is inaction on climate change now a legal liability?

The Court’s advisory opinion affirms that inadequate action on climate change may violate international law. Its findings could shape the contours of debate at COP30.

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Published 1 August 2025 — 4 minute READ

Image — Vanuatu's Climate Change Minister Ralph Regenvanu delivers a speech ahead of the ICJ advisory opinion on states' legal obligations to address climate change, in The Hague on 23 July 2025. (Photo by JOHN THYS/AFP via Getty Images)

Bhargabi Bharadwaj

Research Associate, Environment and Society Centre

Last week, the International Court of Justice (ICJ) issued a unanimous ruling (its ‘advisory opinion’) in response to the questions posed by the UN General Assembly regarding the Obligations of States in respect of Climate Change. 

Many rightfully view the advisory opinion as a milestone in the codification of states’ legal obligations and responsibilities concerning climate change. The ICJ’s advisory opinions are not legally binding, and the Court cannot compel countries to abide by its findings. But the opinion is consequential. Governments’ failure to act on climate change can now be argued to be a breach of law – with potential legal, financial and diplomatic consequences.

That could have significant implications. The threat of exposure to litigation in national courts may help force governments to more urgently reduce emissions and demonstrate their compliance with treaty negotiations. The opinion is also likely to be used as legal precedent in international negotiations and in crafting future treaties. Coming in the lead-up to COP30, scheduled for November in Brazil, it will provide smaller countries with important new leverage.  

The crucial points

For much of its history, the ICJ has maintained a balanced approach and a reluctance to set hard legal boundaries in politically sensitive matters. That approach helped establish its legitimacy as the principal organ for public international law.  

The 2025 climate advisory opinion shows the Court continuing that trend, relying heavily on existing legal norms to cautiously advance state obligations. Its ability to do so reflects increased judicial confidence in addressing risks posed by climate change – as a result of stronger legal frameworks, scientific consensus on climate change impacts, and widespread state practices creating emerging norms and customary international law. 

The opinion finds that international law on climate change is derived from multiple sources, including climate change and environmental treaties, international human rights law and customary international law. And it lays out a number of significant findings. 

The advisory opinion lacks binding force, but its legal significance is far from symbolic. 

The opinion finds that state parties to the Kyoto Protocol must act with due diligence to fulfil the commitments made in the protocol, including common but differentiated responsibilities for high emitters. 

It also finds that state parties to the Paris Agreement are obliged to prepare, communicate and maintain nationally determined contributions (NDCs) which, when taken together, can contain global warming to 1.5°C above pre-industrial levels. The opinion affirms that the International Law Commission’s Articles on Responsibility of States for Internationally Wrongful Acts (2001) applies to climate change law, which will increase certainty when pursuing remedies for environmental harms that cross borders.  

The opinion also enshrines two duties: the first is to prevent significant harm to the environment, embedding a core due diligence standard requiring countries to maintain legal, regulatory, administrative and enforcement measures to achieve rapid and sustained reductions in emissions. 

And the opinion affirms a mandatory duty on states to cooperate internationally, acting in good faith through information-sharing, joint efforts to mitigate the effects of climate change, and transferring the technology needed to achieve the goals of the climate treaties. Both of these duties are customary law, therefore applicable to all states regardless of their signatory status with climate change treaties. 

Can the ICJ enforce these obligations?

The advisory opinion lacks binding force, but its legal significance is far from symbolic. The opinion carries weight as an authoritative interpretation of law, and has the potential to reshape global climate governance as a tool of ‘preventive diplomacy’. 

The legal principles clarified in the opinion are binding as part of international law. For example, it clarifies the core principles of attribution and causation in meeting legal obligations to prevent harm. Just as importantly, the opinion serves as a signal to governments that national and regional policies should align with evolving international legal norms.

By clarifying state responsibilities, the opinion can influence future treaty-making. It will also be hugely influential in shaping future climate-related litigation, allowing claims to be grounded in states’ duties to prevent and repair harms created by climate change based on their conduct, not merely intent. 

That threat of increased legal exposure could play an important role in increasing an incentive for high-emitting economies to raise their environmental standards. 

Legal risk for states and corporations 

The opinion unquestionably expands countries’ legal exposure by confirming that all states have binding duties regardless of their participation in climate treaties. For example, this may still apply to the US despite its withdrawal from the Paris Agreement (though its compliance is unlikely in the short term). 

For businesses, the opinion stops short of creating direct obligations under international law. Instead, it affirms the duty of states to regulate private actors more effectively.

The opinion elevates climate policy from a political commitment to a legal duty, exposing governments to increased legal risk should they fail to regulate emissions adequately, conduct environmental impact assessments, or align their policies with international standards. Failure to perform due diligence – especially concerning fossil fuel production, subsidies, or inadequate climate legislation – will now open the door to claims, besides risking reputational damage. 

For businesses, the opinion stops short of creating direct obligations under international law. Instead, it affirms the duty of states to regulate private actors more effectively – by (for instance) closing regulatory gaps, ensuring businesses internalize risk, and avoiding becoming safe havens for corporate climate irresponsibility.

A lack of clarity on enforcement mechanisms, the voluntary nature of many corporate climate pledges and jurisdictional limits seem to have prevented the court from imposing more stringent obligations on high-emitting corporations. 

Impact on global climate negotiations 

By affirming that action on climate change is a legal obligation grounded in international law and the latest climate science, the opinion clarifies the responsibilities of states – and will likely strengthen the negotiation efforts of low-emitting countries to rally support during COP30. 

The opinion’s application of the law of state responsibility has significant implications. It means that where restitution for a harm caused by a breached obligation is not possible, states must provide compensation. Remarkably, the Court recognized that this compensation may be due for harms causally linked to losses and damages. The ICJ has advised that any injured country can act against any other country that has breached its obligations and caused injury through climate damage.

Low-emitting and climate-vulnerable countries now have a legal basis to demand accountability, support and concrete action from high-emitting countries. 

This could have a significant impact on climate change policymaking this year. The opinion comes just before the countries submit updated NDCs, and in the lead-up to the climate negotiations at COP30 in Brazil. 

Clearly defined obligations by the ICJ could shake up negotiations. Low-emitting and climate-vulnerable countries now have a legal basis to demand accountability, support and concrete action from high-emitting countries. That will inform negotiations on climate finance, equity and justice, addressing losses and damages, and finally, at the final agreement. It could also, potentially, create a freezing effect where countries worried about legal risk back away from high ambition commitments.

While the opinion pressures developed nations, emerging economies are also affected. Countries like India, Brazil and China could face heightened scrutiny, given their current emissions. In their submissions to the Court in November, they emphasized that irrespective of the location of fossil fuel production, consumption – and therefore responsibility – is global. 

In response, the Court emphasized that assigning ‘fair shares’ should be based on the consensus-based structure of the Paris Agreement. 

As climate negotiations intensify, this represents an unresolved tension that is certain to resurface at future COPs, where large developing nations dispute responsibility with historic high emitters – while smaller, more vulnerable countries demand accountability from all.