The UN's International Court of Justice has published its long-awaited advisory opinion on states' responsibilities regarding the climate crisis.

States have a legally binding obligation to prevent climate-related harm and to protect human rights from the impacts of climate change. This is the position of the International Court of Justice (ICJ), the principal judicial organ of the United Nations, based in The Hague, in the Netherlands. The document is an advisory opinion and is therefore non-binding, but it nonetheless carries enormous political weight. It recognises climate change as an "existential threat" and clarifies the obligations and responsibilities of states in this regard.

This process began in 2019 at the initiative of a group of 27 law students from the University of the South Pacific. From this emerged a youth organisation called Pacific Island Students Fighting Climate Change, which joined forces with many others from the four corners of the globe, united under World's Youth for Climate Justice. The idea was to persuade the United Nations to request an advisory opinion from the International Court of Justice on states' responsibilities concerning climate change and human rights.

The government of Vanuatu – a small island nation in the South Pacific that risks disappearing due to rising sea levels – became the champion of the young people's appeal. It led the diplomatic efforts that eventually reached the United Nations General Assembly in New York. On 29 March 2023, the Assembly adopted the resolution requesting the Court to deliver its opinion on two fundamental aspects: the obligations of states to protect the environment and the climate from greenhouse gas emissions under international law, and the legal consequences faced by states that – through their actions or omissions – have damaged the environment and the climate.

Although non-binding, the ICJ's ruling sets out a clear position that cannot be ignored. "The failure of a state to take appropriate action to protect the climate system from greenhouse gas emissions, including through the production of fossil fuels, the consumption of fossil fuels, the granting of fossil fuel exploration licences, or the provision of fossil fuel subsidies, may constitute an internationally wrongful act attributable to that state," said Judge Iwasawa Yuji.

Regarding the damage caused by climate change, he added: "In cases where restitution proves materially impossible, responsible states have an obligation to provide compensation." Possible forms of reparation include halting harmful activities, compensation for climate damage, and the obligation to immediately cease greenhouse gas emissions that exceed the safety threshold indicated by the scientific community. The International Court of Justice went so far as to formulate recommendations on how to ensure climate justice for future generations in the most vulnerable communities.

An advisory opinion does not directly impose obligations or sanctions on specific parties, but rather clarifies how international law frames a given subject – in this case, responsibility for the climate crisis. It will therefore serve as a point of reference for so-called climate litigation, legal actions brought on climate grounds.

"The world's highest court has stated clearly: activities that harm the climate violate international law and people's rights. Governments must reduce emissions to protect people's lives and must compensate for the damage they have already caused," explains Elisa Morgera, UN Special Rapporteur on climate change and human rights. "The right to a clean, safe and healthy environment is inseparable from the right to life, health and dignity. The Court's ruling reflects this truth. The path for major emitters is clear: act now to phase out fossil fuels, support affected communities, and align national laws and finances with international obligations."

Danilo Garrido, legal adviser at Greenpeace International, also believes that "the ICJ's advisory opinion marks a turning point in climate justice, as it has clarified, once and for all, the international climate obligations of states and, even more importantly, the consequences in the event those obligations are violated. This will pave the way for new cases and, hopefully, will bring justice to those who, despite having contributed least to the climate crisis, are already suffering its most severe consequences.