Posse Comitatus
In June 2025, the administration deployed several thousand troops to Los Angeles to support its immigration enforcement actions, sparking protests. California sued, and in early September, a Federal judge ruled that the administration had violated the 1978 Posse Comitatus Act when it used these forces.
Posse comitatus is a Latin phrase meaning “power of the county.” Historically, it referred to the ability of a government authority to summon ordinary citizens to help enforce a law or pursue a criminal. In old western movies, the sheriff would have a ‘posse’ to pursue the bad guys.
Congress passed the Posse Comitatus Act in 1878: “…it shall not be lawful to employ any part of the Army of the United States, as a posse comitatus, or otherwise, for the purpose of executing the laws, except in such cases and under such circumstances as such employment of said force may be expressly authorized by the Constitution or by act of Congress;”
In other words, the military cannot be used as a police force.
Prior to the Act, the military did get involved in domestic affairs. Some instances:
Whiskey Rebellion (1794)
Congress imposed a tax on whiskey in 1791. Farmers used to convert grain into whiskey, which was easier to trade and transport. Farmers in Western Pennsylvania refused to pay the tax, threatened tax collectors, and prepared for armed resistance. President Washington personally led a force of 13,000 soldiers west to enforce the law. The show of force worked, and the farmers backed down. (This was the largest force President Washington ever commanded.)
Nullification Crises (1832 – 1833)
South Carolina and other Southern States opposed the high tariffs passed in the late 1820s. Calling it the ‘Tariff of Abominations,’ South Carolina asserted the right to ‘nullify’ laws it believed unconstitutional and threatened to secede from the Union. President Jackson threatened to send the military to enforce the law, authorized by the ‘Force Bill’ passed by Congress. South Carolina backed down.
Railroad Strike of 1877
Railroad workers went on a nationwide strike in 1877 over wages, halting most railroad traffic. In some cities, the strike turned into riots, resulting in property destruction. President Rutherford Hayes called in Federal troops to restore order and ended the strike.
Post Civil War Reconstruction (1865 – 1877)
Federal Soldier Keeping the Peace During Reconstruction
After the Civil War, Southern Democrats restricted voting rights through intimidation and violence of the recently freed slaves . The Republican-led Congress passed the 1867 Reconstruction Acts, which divided the South into five military districts run by the army. The Army supervised elections to ensure Black men could vote safely. When the South continued its resistance, Congress passed three ‘enforcement’ acts (1870 -71) to prevent voter suppression by increasing penalties, moving jurisdiction away from State Courts to Federal Courts, and allowing the President to use the military to protect Civil Rights.
President U.S. Grant sent Federal troops South to enforce these laws. He declared martial law in areas of the South and sent troops to arrest Ku Klux Klan members. However, with the end of Reconstruction in 1877, the Federal Government withdrew its troops from the South.
Passage of the Posse Comitatus Act - 1878
By the late 1870s, Northerners had grown weary of the ongoing military presence in the South. They were also concerned about Federal power and potential overreach. Southern Democrats wanted to prevent future military intervention. As a result, this act was passed on a bipartisan vote.
Insurrection Act of 1807
The Insurrection Act, along with subsequent amendments, is an exception to the Posse Comitatus Act and allows the Federal Government to deploy the military to enforce laws and maintain the peace.
It consists of three sections.
State Request: A State my request military assistance
The President to deploy forces if ‘unlawful obstructions, combinations, or assemblages, or rebellion against the authority of the United States, make it impracticable to enforce the laws of the United States in any State by the ordinary course of judicial proceedings.’
The Federal Government may intervene if an insurrection or violence deprives the people of their rights and the state is unable or unwilling to protect those rights.
Invocations of the Insurrection Act Since 1878
The Insurrection Act has been used to support the deployment of the military since the passage of the Posse Comitatus Act. Some examples:
Pullman Railroad Strike (1894)
Pullman workers went on strike over wages and the cost of living in the company-owned town of Pullman, near Chicago. The strike went nationwide, disrupting railroad traffic. President Grover Cleveland invoked the Insurrection Act directly using the language of the act:
Whereas, by reason of unlawful obstructions, combinations, and assemblages of persons, it has become impracticable, in the judgment of the President, to enforce by the ordinary course of judicial proceedings the laws of the United States within the State of Illinois, and especially in the city of Chicago within said State.
Governor Altgeld Monument
Governor John Peter Altgeld opposed the intervention, stating that Illinois could handle the disturbances. His grave monument includes part of his message to the President: ‘This is a government of law, and not a government by the caprice of an individual.’
President Cleveland’s intervention broke the strike.
Little Rock (1957)
The 1954 Brown v. Board of Education decision by the Supreme Court banned segregated schools. In 1957, nine black students were selected to integrate an all-white school in Little Rock. Governor Faubus called out the Arkansas National Guard to prevent the black students from entering the school.
President Eisenhower sent in the 101st Airborne Division to escort the children into the school. He used the Insurrection Act to provide the legal authority for his actions,
Universities of Mississippi and Alabama (1962, 1963)
In 1962, James Meredith, an African American man, attempted to enroll at the then all-white University of Mississippi after winning a lawsuit that went to the Supreme Court. Governor Ross Barnett wanted to defy the Court and block his admission. Although Federal forces escorted Meredith, a riot broke out, resulting in two deaths and many injuries. Ultimately, the Federal government needed 31,000 (!) troops to stop the rioting and protect Meredith.
In 1963, two African Americans sought to enter the University of Alabama. Governor George Wallace stood in the doorway, blocking their entrance. When President Kennedy deployed one hundred troops, Wallace backed down. Unlike the prior year at the University of Mississippi, violence was avoided.
Assassination of Martin Luther King (1968)
After the assassination, of Martin Luther King, riots broke out in many cities. President Johnson invoked the insurrection Act and sent troops to several cities experiencing the most violence. In Washington, DC, over 13,000 soldiers were deployed.
Similarly, over 5,000 Federal troops were sent to Chicago and more than 10,000 to Baltimore. In these cities, the local governments requested assistance from the Federal government.
Rodney King – Los Angeles – 1992
In 1992, four white policemen were acquitted of police brutality after beating Rodney King while arresting him. Widespread riots broke out, and the Governor and Mayor requested Federal assistance. Over 10,000 troops were involved in controlling the riots.
Summary
There are times when Federal military intervention has been needed to protect civil rights or control violence and riots when local authorities are overwhelmed. However, the current administration’s use of troops has raised questions over the appropriate use of Federal resources. Ultimately, this issue will be resolved by the courts.