Leisy v. Hardin‪.‬

The power vested in Congress "to regulate commerce with foreign nations, and among the several States, and with the Indian Tribes," is the power to prescribe the rule by which that commerce is to be governed, and is a power complete in itself, acknowledging no limitations other than those prescribed in the Constitution. It is co-extensive with the subject on which it acts and cannot be stopped at the external boundary of a State, but must enter its interior and must be capable of authorizing the disposition of those articles which it introduces, so that they may become mingled with the common mass of property within the territory entered. Gibbons v. Ogden, 9 Wheat. 1; Brown v. Maryland, 12 Wheat. 419.