The International Tribunal for the Law of the Sea (ITLOS) also said that wealthy countries must reduce their emissions faster than developing ones.

The tribunal interprets and upholds the 1982 UN Convention on the Law of the Sea (UNCLOS), an international treaty representing 169 countries.

The statements were made as part of an advisory opinion on climate change yesterday.

The opinion was sought by the Commission of Small Island States on Climate Change and International Law (COSIS), nine Caribbean and Pacific island nations led by Antigua and Barbuda and Tuvalu.

In its opinion, the tribunal noted that the oceans are warming and becoming more acidic due to carbon dioxide emissions from human activities.

Joie Chowdhury, a senior attorney at the Center for International Environmental Law, said: “It’s the first time an international court has unequivocally affirmed that states do not have unfettered discretion, but specific obligations under international law to act urgently, ambitiously and equitably, to protect oceans from the drivers and impacts of climate change.”

ITLOS is one of three courts tasked with producing an advisory opinion on climate change. The International Court of Justice (ICJ) was last year asked for its view on states’ legal duties on the climate emergency. The inter-American Court of Human Rights held the first of several hearings in April.