Explainer: What Is the United States’ Insurrection Act?

Today’s Insurrection Act traces its history to a series of statutes passed between 1792 and 1871 that allow the president to deploy military troops domestically under certain specific conditions. 

The Insurrection Act is an exception to the Posse Comitatus Act, which generally forbids the federal military to engage in law enforcement activities such as enforcing curfews, investigating crimes, or making arrests. 

Under the Insurrection Act, the president can deploy the federal military domestically when:

• there is an insurrection against a state’s government and the state requests assistance;
• there is a rebellion against the federal authority of the United States that makes it impossible to enforce the law through the courts; or
• the president believes a military deployment is necessary because there is insurrection or unlawful activity in a state that (a) hinders the execution of state and the federal law to the extent that it deprives people of a constitutional right and the state is unable or unwilling to protect that right; or (b) obstructs the execution of federal law or impedes the course of justice.

The Insurrection Act is a last resort, used when a threat is too great for local and state authorities to control.

What constitutes insurrection? 

The Insurrection Act does not establish what constitutes an insurrection, but the Merriam Webster dictionary defines the term as an act or instance of revolt against civil authority or an established government.

Is the Insurrection Act only for insurrections? 

The law allows presidential action beyond responding to insurrections. For example, the Act allows the president to act against domestic violence, conspiracy, obstruction, or rebellion if specific conditions are met. These conditions include civil unrest or illegal activity that attacks state governments, the federal government, or individual constitutional rights.

Whenever the president considers it necessary to use the militia or the armed forces under this chapter, he shall, by proclamation, immediately order the insurgents to disperse. 10 USC § 254.

When was the Insurrection Act used previously?

Presidents have used the Insurrection Act when acts of revolt reach a level of violence that makes it impossible for local law enforcement to control. George Washington first invoked a predecessor to the Insurrection Act during the Whiskey Rebellion of 1791–94, in which hundreds of farmers protested a new federal tax on the American production of liquor through violent attacks on tax inspectors and armed riots throughout western Pennsylvania. 

Additionally, a number of military deployments under the Insurrection Act were used to break labor strikes. The National Guard was deployed during the Great Railroad Strike of 1877, in which over 100,000 workers in several states participated. Most of the US rail system could not function, and around 100 people were killed in the violence. The standoff ended after 52 days when the National Guard broke the strike. The 1894 Pullman Strike, another railroad strike in several states that shut down the railroad system, ended with the president sending troops across several states to break the strikes. The federal military broke similar strikes by coal miners in Colorado (1914) and West Virginia (1921). 

Additionally, presidents have invoked the Act in times of racial conflict. President Lincoln invoked the Act at the start of the Civil War in 1861. President Grant invoked it and deployed troops against the Ku Klux Klan in South Carolina in 1871. President Eisenhower used it to take federal control over members of the Arkansas National Guard in 1957 to stop the Arkansas governor from using the state National Guard to prevent Black students from entering a newly desegregated school. The federal military was also deployed in 1968 to suppress riots after Dr. Martin Luther King, Jr.’s assassination. The most recent invocation was during the 1992 Los Angeles riots, when President George H.W. Bush deployed the federal military after several days of rioting in response to the acquittal of four white police officers who had severely beaten Rodney King, Jr. during a traffic stop. 

The Act has not been used in over three decades, no doubt because it is viewed as an extreme measure. For example, today a majority of Americans across party lines believe that the military should not be used to stop people from protesting in the United States. Past administrations and the American public view the Insurrection Act as something to be used with the utmost discretion.