The purpose of the Wilderness Act (Act), 16 U.S.C. §§ 1131 et seq., was to preserve and protect wilderness lands in their natural state. In accordance with this purpose, § 4(c) of the Act prohibited commercial enterprise within any wilderness area. Although the Act did not define “commercial enterprise,” it listed exceptions to the prohibition. Commercial-fishing activities were not included in this list of exceptions. The Alaska Department of Fish and Game (ADFG) conducted a salmon-hatchery project in Tustumena Lake, located in the Kenai Wilderness (wilderness area) and the Kenai National Wildlife Refuge, to research salmon reproduction. In 1993, the ADFG contracted with the Cook Inlet Aquaculture Association (CIAA) to run the ADFG’s hatchery programs. The CIAA was a non-profit corporation that received funding from the commercial salmon industry and the production of hatchery-raised salmon. In 1997, the U.S. Fish and Wildlife Service (FWS) (defendant) issued a permit to the CIAA for the Enhancement Project (project), which involved catching salmon outside the wilderness area, hatching eggs, and releasing salmon into the wilderness area. The FWS determined that the Act was a legislative compromise that did not reflect absolute preservationist values, and that the project was therefore consistent with the Act. The Wilderness Society and others (plaintiffs) challenged the FWS’s permit in district court, claiming that the permit violated the Act. The district court found that the project was not a commercial enterprise, based in part on the FWS’s environmental assessment finding that (1) the project had a benign impact on the wilderness area, (2) the CIAA was a non-profit entity, (3) the State of Alaska (state) heavily regulated the project, and (4) fishermen were catching the salmon outside the wilderness area. The plaintiffs appealed.