In 2025, the International Court of Justice (ICJ) unanimously confirmed that, under international law, states must act now and big polluters must scale up their efforts to address climate change.
States must act now to avoid climate catastrophe
What is the ICJ?
The International Court of Justice is the principal judicial organ of the United Nations. As the world's court, it adjudicates disputes between states and provides advisory opinions on international legal issues.
An advisory opinion from an international court provides guidance on how international law should be understood and interpreted. The court clarifies legal obligations and can shape future laws and court decisions. Seeking an advisory opinion can therefore be a powerful catalyst for lasting change in the international legal system.
Vanuatu ICJ advisory opinion
The Republic of Vanuatu, following an initiative by the youth-led Pacific Islands Students Fighting Climate Change (PISFCC), spearheaded the efforts that led to the UN's landmark International Court of Justice (ICJ) advisory opinion.
In July 2024, ClientEarth joined PISFCC and other organisations in publishing a joint legal memorandum for the ICJ advisory proceedings. The following year, the ICJ unanimously confirmed that states must act now to avoid climate catastrophe under international law.
What this means for the fight against the climate crisis
For ClientEarth, the ICJ's decision marks a significant milestone for climate justice, providing a strong legal basis for holding governments and corporations to account. It strengthens our ability to argue that meaningful climate action is not just a political choice, but a requirement under international law.
The opinion confirms that:
- Governments could be in breach of international law if they fail to curb fossil fuel production and consumption, approve new fossil fuel projects, or continue providing public funding for fossil fuels.
- Countries with the highest historical emissions bear a greater responsibility to address the climate crisis and help limit global warming to 1.5°C.
- States are legally required to regulate the climate impacts of companies and businesses operating within their jurisdiction.
- The human right to a healthy environment is fundamental to human life and states have an obligation under international law to protect it.
- Countries experiencing the worst impacts of climate change may have a pathway to seek reparations from major historical emitters.
This new-found clarity will equip judges with definitive guidance that will likely shape climate cases for decades to come.Lea Main-Klingst, ClientEarth lawyer
Applying this landmark decision
In Germany, we cited the ICJ advisory opinion in fighting a recent €35.2 billion gas subsidy plan approved by the European Commission, for example.
We argue that by subsidising new fossil-gas capacity through a favourably designed security of supply measure, Germany may also be in breach of its obligations under international law. This is supported under the advisory opinion in which the ICJ found that the granting of fossil-fuel subsidies "may constitute an internationally wrongful act attributable to that State".
In July 2026, we launched a landmark human rights legal complaint against the Belgian government over PFAS - or "forever chemicals" - pollution and its impact on people's health.
In our complaint, we relied on the ICJ's finding that a clean, healthy and sustainable environment is essential for the enjoyment of human rights, including the right to health. We argued that Belgium must protect people's health as required under Article 11 of the European Social Charter.
