In recent years, constitutional courts and supreme courts have handed down important decisions on (potentially) insufficient climate protection regulation. This article analyses the climate decision of the German Federal Constitutional Court and discusses its application to biodiversity protection. It shows that despite of clarifications related to the State’s constitutional duty to protect citizens, including future generations, against the risks of climate change, the application of the decision to other urgent environmental problems remains unclear. The German standard of review grants the legislator considerable leeway in case of remaining scientific uncertainty and still relies on a clear quantification of protection needs. In contrast, the Urgenda ruling of the Dutch Supreme Court shows the way how in case of scientific uncertainty (potentially insufficient) environmental protection can be judicially reviewed while safeguarding the margin of appreciation of the legislator at the same time.