For the first time, the United Nations' top court has declared that failing to protect the planet from climate change could breach international law. The highly anticipated advisory opinion delivered in the Hague on Wednesday "is likely to determine the course of future climate action across the world," reports Reuters. The International Court of Justice (ICJ) called climate change an "urgent and existential" threat and emphasized that a "clean, healthy, and sustainable environment" is a fundamental human right, per the AP. "Failure of a state to take appropriate action to protect the climate system ... may constitute an internationally wrongful act," court President Yuji Iwasawa said. What you need to know: