States that the federal government possesses only those powers delegated, or enumerated, to it through the Constitution, and that all other powers are reserved to the states, or to the people. Proposed September 25, 1789; ratified December 15, 1791, 2 years and 2 months later. The Tenth Amendment to the United States Constitution, a part of the Bill of Rights, was ratified on December 15, 1791. It expresses the principle of federalism, whereby the federal government and the individual states share power, by mutual agreement. The Tenth Amendment prescribes that the federal government has only those powers delegated to it by the Constitution, and that all other powers not forbidden to the states by the Constitution are reserved to each state, or to the people. Wiki link