The federal government is a government of delegated powers, meaning that it has only those powers delegated to it by the Constitution. All other powers, the Tenth Amendment reads, “are reserved to the states . . . or to the people.” The powers delegated to the federal government may be exclusive, meaning that they may be exercised only by the federal government, or they may be concurrent, meaning that they can be exercised by both the federal and state governments. While the term “concurrent” is used only in the Eighteenth Amendment, granting both the federal government and the states concurrent authority to enforce Prohibition, other powers may be concurrent if they are not granted exclusively to the federal government by the explicit language of the Constitution, or if the exercise of state authority in the same domain is not incompatible with the exercise of national power.
Deciding which powers are exclusive and which are concurrent is a difficult and continuing undertaking. In the modern period, the issue is usually framed in the context of preemption, and the U.S. Supreme Court has played an important role in determining whether the federal government has “occupied the field” to such an extent that state action in a given area is precluded, effectively making federal authority exclusive.
Last updated: 2006