The Migratory Bird Conservation Act (Conservation Act), 16 U.S.C. §§ 715 et seq., authorized the federal government (plaintiff) to acquire land for use as migratory-bird sanctuaries, subject to state legislative consent. The Migratory Bird Hunting Stamp Act (Stamp Act), 16 U.S.C. §§ 718 et seq., funded these land acquisitions by requiring waterfowl hunters to buy stamps. The Stamp Act was amended in 1958 to allow easement acquisition over wetlands, which was not subject to the Conservation Act’s requirements. The Wetlands Act of 1961 (Loan Act) provided a new income source for wetland acquisition, and required the consent of a state governor or agency prior to acquisition. Between 1961 and 1977, two North Dakota governors consented to the acquisition of federal easements over approximately 1.5 million acres of wetlands. By 1977, the federal government had acquired easements over nearly half of these wetlands. After a dispute with the federal government, the State of North Dakota (state) (defendant) enacted legislation in 1977 that limited easements to 99 years and authorized landowners to drain any after-expanded wetlands. The federal government sued the state in the United States District Court for the District of North Dakota, seeking a declaratory judgment that the 1977 legislation was inapplicable because the 99-year and wetland-draining provisions were hostile to federal law. The district court granted summary judgment for the federal government. The court of appeals affirmed. The state appealed, asserting that the Loan Act’s gubernatorial-consent requirement allowed the at-will revocation of state consent, up until the moment of land acquisition. The United States Supreme Court noted probable jurisdiction over the state’s appeal.