Citizens around the world are asking courts to override the climate-related policy choices of democratically elected legislatures and mandate the substance of future legislation. In the name of previously unrecognized rights, plaintiffs in hundreds of cases are asserting that judges have the authority to command action by their supposedly co-equal legislative and executive branches of government. Whatever the merits of the plaintiffs’ policy objectives, their campaign to circumvent the political branches poses a serious threat to the rule law and the constitutional principle of separation of powers. Since the beginning of the modern environmental movement in the 1970s, environmental advocacy groups in the United States have made regular use of the courts to advance their interests. Generally these environmental lawsuits have claimed government failure to comply with the procedural requirements of the National Environmental Policy Act, other federal legislation addressing specific environmental problems like the Clear Air and Water Acts and the Endangered Species Act, the various public lands management laws, and the Administrative Procedures Act. The result is almost always delay, sometimes leading to …