The top UN court on Wednesday paved the way for the payment of possible reparations to be imposed on countries that breach climate change obligations – on a case-by-case basis.
"The legal consequences resulting from the commission of an internationally wrongful act may include ... full reparations to injured states in the form of restitution, compensation and satisfaction," the court said.
The court added that a "sufficient direct and certain causal nexus" had to be shown "between the wrongful act and the injury".
The International Court of Justice gave the remarks as an advisory opinion in a landmark case about nations’ obligations to tackle climate change and the consequences they may face if they don’t, calling it an “urgent and existential” threat to humanity.
“Failure of a state to take appropriate action to protect the climate system ... may constitute an internationally wrongful act,” court President Yuji Iwasawa said during the hearing.
The non-binding opinion, which runs to over 500 pages, is seen as a potential turning point in international climate law.
The court said a “clean, healthy and sustainable environment” is a human right. Enshrining a sustainable environment as a human right paves the way for other legal actions, including states returning to the ICJ to hold each other to account as well as domestic lawsuits, along with legal instruments like investment agreements.
The case is led by the Pacific island nation of Vanuatu and backed by more than 130 countries.
All UN member states including major greenhouse gas emitters like the United States and China are parties to the court.

Outside the court, climate activists gathered with a banner that read: “Courts have spoken. The law is clear. States must ACT NOW.” The courtroom, known as the Great Hall of Justice, was packed.
After years of lobbying by vulnerable island nations who fear they could disappear under rising sea waters, the UN General Assembly asked the ICJ in 2023 for an advisory opinion, an important basis for international obligations.
A panel of 15 judges was tasked with answering two questions: What are countries obliged to do under international law to protect the climate and environment from human-caused greenhouse gas emissions? Second, what are the legal consequences for governments when their acts, or lack of action, have significantly harmed the climate and environment?
“The stakes could not be higher. The survival of my people and so many others is on the line,” Arnold Kiel Loughman, attorney general of the island nation of Vanuatu, told the court during a week of hearings in December.
In the decade up to 2023, sea levels rose by a global average of around 4.3 centimetres (1.7 inches), with parts of the Pacific rising higher still. The world has also warmed 1.3 degrees Celsius (2.3 Fahrenheit) since pre-industrial times because of the burning of fossil fuels.
Simply having the court issue an opinion is the latest in a series of legal victories for the small island nations.
Earlier this month, the Inter-American Court of Human Rights found that countries have a legal duty not only to avoid environmental harm but also to protect and restore ecosystems. Last year, the European Court of Human Rights ruled that countries must better protect their people from the consequences of climate change.
Read moreSmall island states hail 'historic' victory in UN climate case
In 2019, the Netherlands' Supreme court handed down the first major legal win for climate activists when judges ruled that protection from the potentially devastating effects of climate change was a human right and that the government has a duty to protect its citizens.
(FRANCE 24 with AP and AFP)