. . . an act or instance of revolting against civil authority or an established government.
The Insurrection Act of 1807
The Insurrection Act of 1807 is a United States federal law (10 U.S.C. §§ 251–255; prior to 2016, 10 U.S.C. §§ 331–335; amended 2006, 2007) that empowers the President of the United States to deploy U.S. military and federalized National Guard troops within the United States in particular circumstances, such as to suppress civil disorder, insurrection and rebellion.
The act provides the “major exception” to the Posse Comitatus Act of 1878, which limits the use of military personnel under federal command for law enforcement purposes within the United States.
Before invoking the powers under the Act, 10 U.S.C. § 254 requires the President to first publish a proclamation ordering the insurgents to disperse.