Large flocks of Canadian geese settled within the Commonwealth of Virginia in the 1990s. In response to various nuisances caused by the geese, the U.S. Department of Agriculture (Agriculture Department) (defendant) created a goose-management plan (plan) that called for various measures, including killing the geese. Section 703 of the Migratory Bird Treaty Act (MBTA), 16 U.S.C. § 703, prohibited the taking or killing of migratory birds by a “person, association, partnership, or corporation.” Section 707 of the MBTA, 16 U.S.C. § 707, criminalized violations of the MBTA by a “person, association, partnership, or corporation.” An environmental assessment for the plan concluded that the Agriculture Department needed a permit from the U.S. Department of the Interior (Interior Department) (defendant) prior to taking the proposed measures. The environmental assessment also reflected the Interior Department’s longstanding position that the MBTA applied to federal agencies, including the Interior Department’s Fish and Wildlife Service (FWS). In 1997, the FWS director issued a memo finding that federal agencies were not required to obtain a permit prior to taking or killing migratory birds. The Humane Society of the United States and others (plaintiffs) sued the Agriculture Department and the Interior Department, seeking to enjoin the plan’s implementation. The district court held that § 703 applied to federal agencies, and enjoined the defendants from implementing the plan until they obtained a permit to kill the birds. The defendants appealed, arguing that federal agencies were exempt from § 703 because the federal government was not a person and therefore could not be held criminally liable under § 707 for violations of § 703.