The Tenth Amendment to the U.S. Constitution provides that:

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 was ratified as part of the Bill of Rights in 1791.  It was included in the Bill of Rights in reaction to Anti-federalist claims that the Constitution conferred general police powers on Congress.

As stated by Chief Justice Marshall in McCulloch v. Maryland, 17 U.S. 316, 405 (1819):

This government is acknowledged by all to be one of enumerated powers. The principle that it can exercise only the powers granted to it would seem too apparent… That principle is now universally admitted.

If a power is delegated to Congress in the Constitution, the Tenth Amendment expressly disclaims any reservation of that power to the States; if a power is an attribute of State sovereignty reserved by the Tenth Amendment, it is necessarily a power the Constitution has not conferred on Congress.

The powers reserved to the States have generally been referred to as the Police Powers.

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