in U.S. domestic law, a term used to designate the power exercised by a state or municipal government to enact legislation regulating private interests for the protection of the safety, health, and morals of the people, the prevention of fraud and oppression, and the promotion of the public convenience, prosperity, and welfare.

The precise scope of police power is difficult to define. It covers, for example, the maintenance of the peace by the police; the licensing of some trades and professions; the regulation of rates charged by public service corporations; the regulation of security issues by so-called Blue Sky laws, which are statutes intended to prevent fraud in the sale of stocks and bonds; the regulation of hours of labor; and such health regulations as quarantine and compulsory vaccination.

The police power rests on the general legislative authority, and is limited only by express provisions contained in the U.S. Constitution or in state constitutions. Until 1936 the U.S. Supreme Court closely reviewed state and local police-power regulations to determine whether they were reasonable under the due process clause of the 14th Amendment; frequently the Court invalidated state and local social legislation. In recent decades the Supreme Court and other federal courts have declined to declare such legislation unconstitutional, except in the relatively few cases in which the police power has been exercised inconsistently with provisions of the Bill of Rights protecting freedom of speech or of religion or has failed to protect the procedural rights of citizens to a fair hearing.

The power of the federal government to legislate is neither inherent nor residual, but rests on grants of authority vested by the Constitution. Some of these are general, such as the power to regulate commerce; others are specific, as in the power to coin money and to establish post offices and post roads. Since the 1930s, when the Supreme Court upheld much of the federal legislation contained in the program known as the New Deal, the legislative powers of the federal government usually have been sustained by the courts, adding measurably to the ability of the national government to intervene in areas that were previously reserved for state and local governments through the exercise of the police power.        N.D., NORMAN DORSEN, LL.B.