“Police power” refers to the inherent and general authority of a state government to enact laws to protect the health, safety, and welfare of its citizens. It is among the powers reserved to the states by the Tenth Amendment to the Constitution. In exercising its police power, a state cannot violate provisions of the U.S. Constitution, such as the Bill of Rights or the Commerce Clause. Many U.S. Supreme Court cases involve balancing state police power with federal constitutional requirements.
The federal government has no inherent and general police power. However, through the broad interpretation of the powers it does have, especially the powers to tax and spend and the power to control interstate commerce, the federal government exercises something like a police power.