In United States constitutional law, police power is the capacity of the states to regulate behavior and enforce order within their territory for the betterment of the health, safety, morals, and general welfare of their inhabitants. Under the 10th Amendment to the United States Constitution, the powers prohibited from or not delegated to the Federal Government are reserved to the states respectively, or to the people. This implies that the states do not possess all possible powers, since some of these are reserved to the people.
The exercise of police power can be in the form of making laws, compelling obedience to those laws through legal sanctions, physical means, or other forms of coercion and inducements. Controversies over the exercise of police power, particularly the use of physical means, arise when its exercise by the federal government conflicts with the rights of the states or when its exercise by federal or state authorities conflicts with individual rights and freedoms.
Police powers are, from the point of view of state courts, also restricted by state constitutions. The concept of police power is used by federal courts which do not have jurisdiction to interpret state constitutions: from the point of view of federal constitutional law, states have general police powers except where restricted by the federal Constitution.
Because the Congress has limited powers granted in the Constitution, the Federal government does not have a general police power, as the states do. The exceptions are laws regarding Federal property and the military; the Federal government was also granted broad police powers by the Interstate Commerce Act of 1887.
See also 
- United States Constitution
- Eminent domain
- Jacobson v. Massachusetts
- Peace, order and good government
- "Police Power". Encyclopædia Britannica. Retrieved 2007-02-08.