“ To permit the states and their instrumentalities to import commodities for their own use, regardless of the requirements imposed by the Congress, would undermine, if not destroy, the single control which it was one of the dominant purposes of the Constitution to create. It is for the Congress to decide to what extent, if at all, the states and their instrumentalities shall be relieved of the payment of duties on imported articles. ”

“ The control of importation does not rest with the state but with the Congress. In international relations and with respect to foreign intercourse and trade the people of the United States act through a single government with unified and adequate national power. There is thus no violation of the principle which petitioner invokes, for there is no encroachment on the power of the state as none exists with respect to the subject over which the federal power has been exerted. ”

“ The power is buttressed by the express provision of the Constitution denying to the States authority to lay imposts or duties on imports or exports without the consent of the Congress. Article 1, § 10, cl. 2.
The Congress may determine what articles may be imported into this country and the terms upon which importation is permitted. No one can be said to have a vested right to carry on foreign commerce with the United States. ”