Passed by Congress: 25 September 1789
Ratified: 15 December 1791
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.
The Tenth Amendment establishes a strong principle of states' rights in the Constitution. Any powers not explicitly given to the federal government can be assumed to belong to the states, or directly to the people.