Under the Endangered Species Act, when an animal is classified as “endangered,” the Secretary of the Interior must then designate the “critical habitat” of that animal for protection. In 2001, the dusky gopher frog was classified as endangered. The Secretary then designated the four areas where the frogs currently lived as critical habitats, along with another area, dubbed “Unit 1,” where the frogs had not lived for decades and had since been changed from an open-air canopy forest (where the frogs must live) to a closed-canopy timber plantation. The designation of Unit 1 as a critical habitat would cause millions of dollars in losses to the owners of Unit 1. Those owners sued in federal court, but the trial court and the Fifth Circuit held that the designation was appropriate, and the Secretary’s decision not to exclude Unit 1 from the designation was not judicially reviewable. The Supreme Court, in a unanimous opinion (sans Justice Kavanaugh) by Chief Justice Roberts, vacated and reversed. First, the Court held that a “critical habitat” must, by extension, also be a currently inhabitable by the endangered animal as a habitat—if the frogs could no longer live in Unit 1 due to the changes made, it would not be a habitat and, thus, could not be a critical habitat. Second, the Court held that the Secretary’s decision not to exclude Unit 1 from the designation was reviewable by the courts, given that the Act explicitly sets forth a cost/benefit analysis for the Secretary to follow and for the courts to evaluate. The Court remanded the case to the Fifth Circuit to reconsider the case anew given these rulings. The opinion in Weyerhaeuser Co. v. U.S. Fish and Wildlife Service can be read here.