Article I, Section 8, Clause 17:
[The Congress shall have Power . . .] To exercise exclusive Legislation in all Cases whatsoever, over such District (not exceeding ten Miles square) as may, by Cession of particular States, and the Acceptance of Congress, become the Seat of Government of the United States, and to exercise like Authority over all Places purchased by the Consent of the Legislature of the State in which the Same shall be, for the Erection of Forts, Magazines, Arsenals, dock-Yards, and other needful Buildings;–And . . .
For more than a century the Supreme Court kept alive, by repeated dicta, 1 the doubt expressed by Justice Story
whether Congress are by the terms of the Constitution, at liberty to purchase lands for forts, dockyards, etc., with the consent of a State legislature, where such consent is so qualified that it will not justify the 'exclusive legislation' of Congress there. It may well be doubted if such consent be not utterly void. 2 But when the issue was squarely presented in 1937, the Court ruled that, when the United States purchases property within a state with the consent of the latter, it is valid for the state to convey, and for the United States to accept,
concurrent jurisdiction over such land, the state reserving to itself the right to execute process
and such other jurisdiction and authority over the same as is not inconsistent with the jurisdiction ceded to the United States. 3 The holding logically renders the second half of clause 17 superfluous. In a companion case, the Court ruled further that even if a general state statute purports to cede exclusive jurisdiction, such jurisdiction does not pass unless the United States accepts it. 4