Resolved, That the several States composing the United States of America, are not united under the principle of unlimited submission to their general government; but that, by a compact under the style and title of a Constitution for the United States, and of amendments thereto, they constituted a general government for special purposes — delegated to that government certain definite powers, reserving, each State to itself, the residuary mass of right to their own self-government, and that whensoever the general government assumes undelegated powers, its acts are unauthoritative, void, and of no force. . . .
Thomas Jefferson, Kentucky Resolutions (November 1798).