Abstract Litigation has played a central role in the development of regulations concerning greenhouse gas (GHG) emissions in the United States. A 2007 decision of the United States Supreme Court declared that the Environmental Protection Agency (EPA) has authority to regulate GHGs under the Clean Air Act. This ruling became the principal basis for most of the US climate regulations that followed at the federal level. All of the regulations that emerged have been the subject of large volumes of lawsuits claiming they are invalid; so far most of these regulations have survived these attacks. Litigation is also frequently used to challenge specific projects. Outside of the United States, the volume of climate-related litigation is much smaller, and it has tended to involve only particular projects or the administration of emissions trading systems; there have been very few cases that have broad significance to GHG regulation. However, a decision was issued by a Dutch court in June 2015, which, if it survives appeal and is followed elsewhere, will have major importance.