The Migratory Bird Treaty Act (MBTA), 16 U.S.C. § 703, created both felony and misdemeanor offenses for the sale of the body parts of protected birds. Wulff (defendant) was charged under the felony provision for selling a necklace made of protected bird parts to a federal agent. The federal district court granted Wulff’s motion to dismiss the indictment on the ground that, because the felony provision lacked a requirement of guilty knowledge, or “scienter,” a conviction would violate Wulff’s constitutional due process rights. The district court therefore ruled that Wulff, if convicted, would be sentenced under the terms of the misdemeanor provision of the MBTA. The United States (plaintiff) appealed to the United States Court of Appeals for the Sixth Circuit.