Twenty-one young plaintiffs sue the feds, including the President, claiming the gov’t exposed them to the dangers of climate change in violation of their constitutional right to inherit a “well-stewarded” climate. They ask the court to order the feds to immediately cease “authorizing” the use of fossil fuels and to “swiftly phase out” all domestic carbon dioxide emissions, among other things. District court: The lawsuit will proceed to discovery and then to trial. Feds: That is so outrageously wrong that a (rare and extraordinary) mandamus order terminating the suit is appropriate. Ninth Circuit: The suit can proceed.