Martial Law
government by arbitrary military power, superseding municipal, or State law, when the State is imperilled from without or within and the regular administration is unequal to the task of securing general safety.
Martial law is declared to enforce extraordinary measures. It is not a law, as commonly understood, but an abrogation of law, having no legislative sanction.
The U. S. Supreme Court has held that a State legislature may proclaim its existence, should the safety of the public demand it. The Constitution tacitly permits its proclamation in the clause providing that privileges of the writ of habeas corpus should not be suspended, except when necessary in the case of rebellion and invasion.