In this case, the Court unanimously held that the petitioners had standing to seek judicial review of a "Biological Opinion" issued by the Fish and Wildlife Service, under the citizen-suit provision of the Endangered Species Act (ESA) and the Administrative Procedure Act (APA).The Biological Opinion concluded that the long-term operation of the Klamath Project, a series of lakes, rivers, dams, and irrigation canals administered by the Bureau of Reclamation, was likely to jeopardize the continued existence of two endangered species of fish. The Opinion recommended that the Bureau protect these fish by maintaining minimum water levels on certain bodies of water. The Bureau agreed to follow this suggestion. Petitioners, who have competing economic and other interests in Klamath Project water, alleged that the Service's determination that the endangered fish were in jeopardy violated Section 7 of the ESA, that the minimum water level recommendation violated Section 4 of the ESA, and that each action was arbitrary and capricious under the APA. They further claimed that they had standing to bring these claims because the minimum water levels threatened to reduce their irrigation water supply.
The Court first considered whether petitioners' standing under the ESA's citizen-suit provision was to be evaluated under the prudential principle that a "grievance must arguably fall within a zone of interests protected or regulated by the statutory provision . . . invoked in the suit." The Ninth Circuit had ruled that the zone-of-interests standard applied to claims brought under this provision and that the petitioners' claims fell outside the zone of interests protected by the ESA. The Supreme Court, however, held that the breadth of this citizen-suit provision (authorizing "any person" to "commence[e] a civil suit") indicated that Congress had determined that the zone of interests test was not to be the measure of standing under the ESA.
The Court also concluded that the petitioners had standing under Article III. The Court held that at the pleading stage, an alleged reduction in irrigation water supply constituted an "injury-in-fact." Under the "relatively modest" causation standard in place at this stage of litigation, the Court further found that this injury was "fairly traceable" to the issance of the Biological Opinion and was likely to be "redressed" if the Opinion was set aside. The Court noted that judicial review of the petitioners' claims was authorized under two different federal statutes: while the petitioners' Section 4 claim was reviewable under the citizen-suit provision contained in the ES, their Section 7 claim was reviewable only under the APA.