Reserved and Concurrent Powers

The Constitution grants the federal government specific, enumerated powers and leaves the rest to the states and the people. The Tenth Amendment, ratified on December 15, 1791, as part of the Bill of Rights, makes this explicit: 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. Some powers are exclusively federal, such as coining money, declaring war, making treaties, and regulating foreign commerce, and the Constitution expressly forbids states from exercising them.

Reserved powers include the broad police power to protect public health, safety, welfare, and morals, which underlies most criminal law, family law, property law, land use, licensing of professions, public education, and the conduct of elections. Concurrent powers are those both levels of government may exercise at the same time, including taxing, borrowing, establishing courts, making and enforcing laws, and chartering banks and corporations. When federal and state laws on a concurrent matter conflict, valid federal law prevails under the Supremacy Clause.

The Supreme Court once described the Tenth Amendment as a truism that adds nothing to the Constitution's structure, in United States v. Darby in 1941, but since the 1990s it has used the amendment and related principles to protect state sovereignty, holding in New York v. United States in 1992 and Printz v. United States in 1997 that Congress cannot commandeer state legislatures or officials. Supporters of strong reserved powers say they keep government close to the people and let states experiment, while critics say they have historically been invoked to resist civil rights and national standards.