Pursuant to the Endangered Species Act of 1973 (ESA), 16 U.S.C. § 1531 et seq., the Bureau of Reclamation (Bureau) notified the Fish and Wildlife Service (FWS) (defendant) that a large land-reclamation program administered by the Bureau in northern California and southern Oregon might adversely affect two endangered species of fish. As required by the ESA, the FWS provided a report (Biological Opinion) that (1) concluded the project might threaten the two endangered species and (2) recommended feasible options for avoiding the threatened harm. The FWS also issued an Incidental Take Statement (ITS) that allowed the Bureau to cause some harm to the endangered species, as long as the Bureau complied with the Biological Opinion’s recommendations. The Bureau agreed to comply with these recommendations. Two Oregon irrigation districts, along with Brad Bennett and other ranchers within those districts (plaintiffs), filed suit against the FWS and various government officials (defendants), alleging that the Biological Opinion was issued in violation of the ESA and the Administrative Procedure Act (APA), 5 U.S.C. § 551 et seq. The district court dismissed the complaint, and the court of appeals affirmed. The United States Supreme Court granted certiorari.