At a time when the international community is holding climate change conferences and Congress debates on cap-and-trade, new fuel standards, and subsidies for “green” companies, some still feel that political solutions to global warming are not moving fast enough. In the present case, a group of eight states and New York City sued several public utilities companies, alleging that their carbon dioxide emissions contribute to global warming. This is the third major lawsuit to push global warming into the courts (another being Comer v. Murphy Oil USA, in which Cato also filed a brief). All of these suits try to use the common law doctrine of nuisance — the same thing that lets you sue your neighbor if his contaminated water flows onto your land and kills your lawn — to attack carbon emitters. Cato’s brief argues that the chain of causation between the utility companies’ carbon emissions and the alleged harm caused by global warming is so attenuated that it resembles the famed “butterfly effect.” Just as butterflies should not be sued for causing monsoons, six utility companies in the Northeastern United States should not be sued for the complex (and disputed) harms of global warming. In legal terms, the plaintiffs here lack standing to bring such claims. Second, we contend that, even if causation is demonstrable, it is unconstitutional for courts to make complex policy decisions that should be left to the legislature — and this is true regardless of the science regarding global warming. Just as it’s unconstitutional for a legislature to pass a statute punishing a particular person (bill of attainder), it’s unconstitutional — under the “political question doctrine” — for courts to determine wide-ranging policies in which numerous considerations must be weighed against each other in anything but a bilateral way. Nevertheless, the Second Circuit allowed the suit to proceed because the plaintiffs did not ask the court “to fashion a comprehensive and far-reaching solution to global climate change.” We point out that resolving this case while avoiding those comprehensive and far-reaching implications is impossible and that the Constitution prohibits the judicial usurpation of roles assigned to the other, co-equal branches of government.