priate to any of the ends of the government, and within the constitutional range of its powers.[1] So congress possess power to punish offences committed on board of the public ships of war of the government by persons not in the military or naval service of the United States, whether they are in port, or at sea; for the jurisdiction on board of public ships is every where deemed exclusively to belong to the sovereign.[2]
§ 1252. And not only may implied powers, but implied exemptions from state authority, exist, although not expressly provided for by law. The collectors of the revenue, the carriers of the mail, the mint establishment, and all those institutions, which are public in their nature, are examples in point. It has never been doubted, that all, who are employed in them, are protected, while in the line of their duty, from state control; and yet this protection is not expressed in any act of congress. It is incidental to, and is implied in, the several acts, by which those institutions are created; and is preserved to them by the judicial department, as a part of its functions.[3] A contractor for supplying a military post with provisions cannot be restrained from making purchases within a state, or from transporting provisions, to the place, at which troops are stationed. He could not be taxed, or fined, or lawfully obstructed, in so doing.[4] These incidents necessarily flow from the supremacy of the powers of the Union, within their legitimate sphere of action.
§ 1253. It would be almost impracticable, if it were not useless, to enumerate the various instances, in