On May 26, 2020, the Ninth Circuit remanded an important climate-change lawsuit to the district court, directing it to reconsider whether it should have remanded the case to California state court. The cities of San Francisco and Oakland sued five companies that produce oil and natural gas. The district court dismissed the cities’ claims because (1) they are displaced by federal common law, (2) the Clean Air Act displaces any federal common-law claim directed at domestic fossil-fuel emissions, and (3) any federal common-law claim directed at foreign emissions interferes with the separation of powers and the nation’s foreign policy. WLF filed an amicus brief urging the appeals court to affirm the district court’s merits ruling. In its brief, WLF argued (1) that the cities cannot establish proximate cause and (2) that the Court should not deviate from the traditional proximate-cause rule.