One of the world’s most vulnerable countries to the fallout from climate change has won a landmark legal battle, giving countries new ammunition to pursue some of the planet’s biggest emitters.

The United Nations’ top court in a landmark advisory opinion says countries could be in violation of international law if they fail to take measures to protect the planet from climate change, and nations harmed by its effects could be entitled to reparations.

On July 23rd, after two years and an unprecedented number of submissions from governments and international institutions, the court delivered a unanimous verdict. In its opinion, climate change constitutes an “urgent and existential threat” that states must protect people from.