Explainers/Executive
The Insurrection Act, explained: when a president can deploy troops inside the United States
A set of 1790s and Reconstruction-era statutes is the main exception to the law that keeps the military out of civilian law enforcement. Here is what it allows and what limits it.
8 min read|Updated August 5, 2026
Federal law generally bars the Army, Air Force, Navy, Marine Corps and Space Force from enforcing civilian law. That rule comes from the Posse Comitatus Act of 1878. The Insurrection Act, now codified at 10 U.S.C. sections 251 through 255, is the principal statutory exception. It lets the president deploy federal troops or federalize the National Guard to suppress an insurrection, enforce federal law, or protect constitutional rights when a state cannot or will not. The statute has been invoked roughly 30 times, most recently in 1992 during the Los Angeles riots at the request of California's governor.
- Where it lives in law
- 10 U.S.C. sections 251-255, built from the Calling Forth Act of 1792, the Insurrection Act of 1807 and Reconstruction statutes including the Ku Klux Klan Act of 1871.
- Baseline rule
- The Posse Comitatus Act, 18 U.S.C. 1385, makes it a crime to use the Army or Air Force to execute civilian law except where Congress or the Constitution authorizes it.
- Three triggers
- A state legislature or governor requests help (section 251); obstruction makes it impracticable to enforce federal law (section 252); or a state deprives people of constitutional rights and fails to protect them (section 253).
- Required first step
- Section 254 directs the president to first issue a proclamation ordering the participants to disperse.
- Last invoked
- 1992, when President George H.W. Bush deployed federal troops in Los Angeles at Governor Pete Wilson's request. It was not invoked in 2020.
What does the Posse Comitatus Act actually prohibit?
It makes it a federal crime to willfully use the Army or the Air Force to execute the laws — meaning to arrest, search, seize or otherwise perform civilian police functions — unless Congress or the Constitution expressly authorizes it. Department of Defense regulation extends the same restriction to the Navy and Marine Corps, and later law added the Space Force. It does not bar the military from providing equipment, training, intelligence support or disaster relief, and it does not apply to the National Guard when the Guard operates under state control.
What are the National Guard's three legal statuses?
State active duty means the governor commands and the state pays; Posse Comitatus does not apply. Title 32 status means the governor still commands but the federal government pays, which is common for border and disaster missions; Posse Comitatus still does not apply. Title 10 status means the Guard is federalized under presidential command, and Posse Comitatus does apply unless a statute such as the Insurrection Act lifts it. Which status troops are in determines who can give them orders and what they can lawfully do.
What does each Insurrection Act section authorize?
Section 251 lets the president federalize the militia when a state legislature, or the governor if the legislature cannot convene, requests help against an insurrection. Section 252 lets the president use the armed forces or federalized militia when unlawful obstructions or rebellion make it impracticable to enforce U.S. law through ordinary judicial proceedings; no state request is required. Section 253 covers insurrection or violence that deprives a class of people of constitutional rights when state authorities fail to protect them, which is the provision used for civil rights enforcement in the 1950s and 1960s.
When has it been used?
Notable uses include the Whiskey Rebellion in 1794, Reconstruction enforcement against the Ku Klux Klan in South Carolina in 1871, the 1957 desegregation of Central High School in Little Rock, the 1962 integration of the University of Mississippi, the 1963 University of Alabama enrollment, riots after the assassination of Martin Luther King Jr. in 1968, and the 1992 Los Angeles riots. Some of those deployments were over a governor's objection; others came at a governor's request.
What checks exist on it?
The statute gives the president broad discretion and uses terms such as insurrection, rebellion and domestic violence that Congress never defined. In Martin v. Mott (1827) the Supreme Court held that the president's judgment about whether the conditions exist is largely conclusive, though the Court has never squarely reviewed a modern invocation. The practical constraints are political and institutional: the required dispersal proclamation, congressional oversight and appropriations, military leaders' obligation to refuse unlawful orders, and lawsuits over specific actions taken by deployed troops rather than over the decision to deploy.
Have there been efforts to change it?
Yes. Bipartisan proposals over the past several years, including from the Brennan Center and members of both parties, would define the triggering terms, require consultation with Congress, impose a time limit such as 30 days unless Congress authorizes an extension, and provide expedited judicial review. None has become law, so the 19th-century text remains in force.