The U.S. secretary of the interior (secretary) (defendant) was granted decision-making authority over the permitting process for livestock grazing by the Taylor Grazing Act of 1934 (Act), 43 U.S.C. §§ 315 et seq. The U.S. Department of the Interior’s grazing regulations allowed the secretary to cancel grazing permits and reduce each permit’s animal unit month (AUM) grazing allocation. The Act authorized the secretary to reclassify and withdraw land used for livestock grazing. However, the Act required the secretary to adequately safeguard grazing privileges in a manner that was “consistent with the purposes and provisions” of the Act. The Act’s purposes included both livestock-industry stabilization and overgrazing prevention. The Act also stated that grazing permits did not create a “right, title, interest or estate” in or to grazing lands. In 1995, the grazing regulations were revised to define “grazing preference” in reference to a priority, rather than a number of AUMs. The revised regulations also defined the term “permitted use” as forage allocated by or under the guidance of a land-use plan. Public Lands Council and other nonprofit ranching organizations (plaintiffs) filed suit against the secretary and others (defendants), challenging the regulations for failing to safeguard grazing privileges. The district court ruled that some of the regulations were unlawful. The court of appeals reversed. The United States Supreme Court granted certiorari.