Appellee bait dealer (appellee) arranged to have live baitfish imported into Maine, despite a Maine statute prohibiting such importation. He was indicted under a federal statute making it a federal crime to transport fish in interstate commerce in violation of state law. He moved to dismiss the indictment on the ground that the Maine statute unconstitutionally burdened interstate commerce, and Maine intervened to defend the validity of its statute. After an evidentiary hearing, the District Court denied the motion to dismiss and held the state statute constitutional. The court found that substantial uncertainties surrounded the effects that baitfish parasites and non-native species would have on the State's wild fish population, and that less discriminatory means of protecting against those threats were currently unavailable. Appellee then entered a conditional guilty plea, reserving the right to appeal the District Court's constitutional ruling. The Court of Appeals reversed, concluding that the state statute was unconstitutional. The Supreme Court held that the ban did not violate the commerce clause in that it served legitimate local purpose, i.e., protecting native fisheries from parasitic infection and adulteration by non-native species that could not adequately be served by available non discriminatory alternatives.

Appellee bait dealer (appellee) arranged to have live baitfish imported into Maine, despite a Maine statute prohibiting such importation. He was indicted under a federal statute making it a federal crime to transport fish in interstate commerce in violation of state law. He moved to dismiss the indictment on the ground that the Maine statute unconstitutionally burdened interstate commerce, and Maine intervened to defend the validity of its statute. After an evidentiary hearing, the District Court denied  the motion to dismiss and held the state statute constitutional. The court found that substantial uncertainties surrounded the effects that baitfish parasites and non-native species would have on the State's wild fish population, and that less discriminatory means of protecting against those threats were currently unavailable. Appellee then entered a conditional guilty plea, reserving the right to appeal the District Court's constitutional ruling. The Court of Appeals reversed, concluding that the state statute was unconstitutional.