In a historic development for climate accountability, the International Court of Justice (ICJ), also known as the UN’s top court, has delivered a landmark advisory opinion on nations’ legal obligations to address climate change, marking a pivotal moment in international law and environmental governance.

This is the first time the ICJ has weighed in so directly on the climate crisis, and its ruling is expected to have far-reaching implications for governments, corporations, and global policy-making.

Background to the Case

The advisory opinion stems from a UN General Assembly resolution passed in 2023, which requested the ICJ to clarify how international laws—particularly human rights and environmental treaties—apply to climate change responsibilities. The resolution, spearheaded by Vanuatu and other Pacific Island nations, received overwhelming support from member states, highlighting the growing urgency for legal frameworks to back climate action.

The request posed two main questions:

1. What are states' obligations under international law to ensure the protection of the climate system?

2. What are the legal consequences for states that fail to meet these obligations?

After months of written submissions and public hearings involving over 80 countries and global organisations, the ICJ has delivered its formal opinion.

What the ICJ Ruled

The court concluded that states have binding legal obligations under existing international law to protect the environment, particularly in the context of global warming and its effects on human rights.

The ruling asserts that:

• Climate change poses a real and imminent threat to basic human rights, including the rights to life, health, food, and adequate housing.

• States must take active, measurable steps to reduce greenhouse gas emissions, in line with international agreements such as the Paris Climate Accord.

• High-emitting nations bear a greater legal responsibility, given their historical and ongoing contributions to climate change.

• Failure to act may lead to legal consequences under international human rights law and environmental treaties, particularly where climate inaction results in harm to other nations or vulnerable populations.

The Legal Weight of the Opinion

While the ICJ’s opinion is non-binding, it carries significant legal and moral authority, particularly within the UN system. International courts and tribunals, national judges, and policy negotiators are likely to refer to this ruling as a key interpretative tool in future climate-related cases and treaties.

Legal scholars suggest that the opinion could pave the way for:

• New climate litigation against states or corporations in domestic and international courts.

• Strengthened national climate legislation, particularly in countries with climate justice movements.

• More pressure on industrialised nations to compensate vulnerable countries suffering from the effects of climate change.

A Victory for Climate-Vulnerable Nations

The advisory opinion has been widely welcomed by climate-vulnerable nations, particularly small island developing states, which face rising sea levels, extreme weather, and food insecurity as a direct result of global warming.

In a statement, the Prime Minister of Vanuatu called the ruling a “massive victory for climate justice”, adding that it gives legal support to the moral claims these countries have long made at climate conferences.

Pacific Island nations, African countries, and youth climate groups have hailed the ICJ’s move as a powerful step toward holding polluters accountable, and as an instrument to compel global action.

International Reactions Mixed

Developing nations and civil society organisations were quick to celebrate the opinion. However, major industrialised countries, while accepting the court’s authority, responded more cautiously.

Some nations reportedly expressed concerns during hearings about the opinion’s possible influence on future liability and climate-related lawsuits. Legal analysts suggest that countries like the United States, China, and Russia may now face increased scrutiny for their climate policies—or lack thereof.

Nevertheless, the court made it clear that economic considerations cannot override fundamental obligations to protect people and the planet.

A Turning Point for Climate Accountability

This opinion is likely to reshape how climate responsibility is understood in international law, giving legitimacy to arguments that climate inaction is not just irresponsible, but legally questionable.

It could also bolster the ongoing push for a Fossil Fuel Non-Proliferation Treaty, currently being proposed by several nations and supported by a growing number of cities and NGOs.

In parallel, climate activists say they are now better positioned to take legal action against corporations and governments that fail to meet emission targets or violate environmental commitments.

Looking Ahead: Pressure on COP and G20

The ICJ opinion is expected to feature prominently in the upcoming UN Climate Change Conference (COP31), as well as in discussions at the G20 summit, where climate finance, emissions reductions, and green technology transfer will be high on the agenda.

For policymakers, the message from the world’s highest court is now clear:
Climate inaction can carry legal consequences, and states are bound by more than just political promises—they are bound by law.