15 December 1791
The Tenth Amendment helps to define the concept of federalism, the relationship between Federal and state governments. As Federal activity has increased, so too has the problem of reconciling state and national interests as they apply to the Federal powers to tax, to police, and to regulations such as wage and hour laws, disclosure of personal information in recordkeeping systems, and laws related to strip-mining. [Cornell]
Amendment X
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.