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.

A closely-watched international climate case that could yield guidance for governments around the world wrapped its first week of arguments before the top court of the United Nations in The Hague Friday.

The top United Nations court has taken up the largest case in its history, hearing the plight of several small island nations helpless in combating the devastating impact of climate change.