The ESA seeks to protect species of animals against threats of extinction caused by man. The ESA instructs the Secretary of the Interior to promulgate by regulation a list of those species which are either endangered or threatened under enumerated criteria, and to define the critical habitat of these species. Each Federal agency must then ensure that any action authorized, funded, or carried out by it is not likely to jeopardize the continued existence of any endangered species or threatened species. In 1978, the Fish and Wildlife Service (FWS) and the National Marine Fisheries Service (NMFS) promulgated a joint regulation stating that the obligations imposed by 7(a)(2) extend to actions taken in foreign nations. The next year the Interior Department issued a reinterpretation of Section 7 (a)(2) of the Endangered Species Act of 1973 (ESA). It held that it only applied to actions taken in the United States and on the high seas. The Defenders of the Wildlife (P) filed this action seeking a declaratory judgment and an injunction that the Secretary of the Interior apply the old interpretation of that section (it applies to foreign nations). The District Court granted the Secretary's motion to dismiss for lack of standing. The Court of Appeals reversed by a divided vote. On remand, the Secretary moved for summary judgment on the standing issue, and respondents moved for summary judgment on the merits. The District Court denied the Secretary's motion. The Eighth Circuit affirmed. The Supreme Court granted certiorari. The Court of Appeals gave the plaintiff's standing based on a procedural injury from the citizenship provisions in the ESA.