Posse Comitatus Act: Can US Troops Be Deployed on American Soil?

The Posse Comitatus Act and the Insurrection Act of 1807 define and limit the power of the federal government to use U.S. military troops to enforce the law or federal domestic policy within the borders of the United States.

The Posse Comitatus Act

The Posse Comitatus Act prohibits the use of forces of the U.S. Army, Air Force, Navy, or Marines to enforce federal, state, or local laws anywhere on American soil unless authorized to do so by the Constitution or an act of Congress. The Posse Comitatus Act, however, does not prevent state National Guard units from assisting law enforcement within their home state or an adjacent state when requested by the state’s governor, or when placed under federal control through the presidential invocation of the Insurrection Act of 1807.

The Insurrection Act

The Insurrection Act of 1807, as an emergency exception to the Posse Comitatus Act, empowers the president of the United States to deploy both the regular U.S. military and the active-duty National Guard—under temporary federal control—within the United States in certain extreme or emergency circumstances, such as rioting, insurrection, and rebellion.

It was first invoked during conflicts with Native Americans during the 19th century. Both presidents Eisenhower and Kennedy invoked the act to help state police enforce court-ordered racial desegregation in the South. More recently, the act was invoked by George H.W. Bush to deal with riots and looting in the aftermath of Hurricane Hugo in 1989 and during the 1992 Los Angeles riots. 

Can Presidents Act Alone in Deploying the Military?

Many legal experts have agreed that the Insurrection Act does empower U.S. presidents to bypass Congress in deploying the regular military on American soil to intervene in cases of civil disobedience.

For example, Harvard University law professor Noah Feldman has stated that the “broad language” of the Insurrection Act allows the use of the military when necessary to prevent acts “obstructing the execution of federal law to the extent that local police and the National Guard can’t successfully stop violence on the streets,” such as rioting and looting.

What the National Guard and Military Can Do on US Soil

The Posse Comitatus Act, the Insurrection Act, and National Guard policy place limits on the actions of National Guard forces when federalized and deployed by order of the president. In general, forces of the regular U.S. military and National Guard are limited to providing support and assistance to local and state law enforcement and public safety agencies. Such assistance typically includes protecting human life, protecting public and private property, and restoring and maintaining civil order. For example, the National Guard Reaction Force assists local police with activities such as providing site security, manning roadblocks and checkpoints, and protecting public and private property, including preventing looting.

What the Regular Military Cannot Do on US Soil

Under the Posse Comitatus Act as reflected in Department of Defense (DoD) policy, regular military forces, while deployed on U.S. soil, are prohibited from performing several traditional law enforcement activities other than in a support role, including:

• Carrying out actual apprehensions, searches, questioning, and arrests
• Using force or physical violence
• Brandishing or using weapons except in self-defense, in defense of other military personnel, or defense of non-military persons, including civilian law enforcement personnel

Use of the Military and the Right to Protest

While freedom of speech and the right to assemble and express opinions through protest is specifically protected by the First Amendment to the U.S. Constitution, the government is allowed to restrict, even suspend these rights in certain circumstances.

In most cases, the rights to assemble and protest may be restricted or suspended when a protest event does or is considered likely to result in violence that endangers human life and safety, violations of the law, threats to national security, or damage to property, such as looting or arson. In essence, freedom can end where rioting begins.

However, peaceful assembly and protest that does not involve violence, civil disobedience, or the willful violation of the laws of the state may not be legally restricted or suspended. In common practice, shutting down a protest by law enforcement is done only as a “last resort.” Neither the police nor the military have the constitutional authority to disperse protest gatherings that do not pose a clear and present danger of riot, civil disorder, interference with traffic, or other immediate threat to public safety or national security.

Sources and Further Reference

• “The Posse Comitatus Act.” U.S. Northern Command, Sept. 23, 2019, https://www.northcom.mil/Newsroom/Fact-Sheets/Article-View/Article/563993/the-posse-comitatus-act/.
• “The Posse Comitatus Act and Related Matters: The Use of the Military to Execute Civilian Law.” Congressional Research Service, November 6, 2018, https://fas.org/sgp/crs/natsec/R42659.pdf.
• Banks, William C. “Providing Supplemental Security—The Insurrection Act and the Military Role in Responding to Domestic Crises.” Journal of National Security Law & Policy, 2009, https://jnslp.com/wp-content/uploads/2010/08/02-Banks-V13-8-18-09.pdf.
• Hurtado, Patricia and Van Voris, Bob. “What the Law Says About Deploying Troops on U.S. Soil.” Bloomberg/Washington Post, June 3, 2020, https://www.washingtonpost.com/business/what-the-law-says-about-deploying-troops-on-us-soil/2020/06/02/58f554b6-a4fc-11ea-898e-b21b9a83f792_story.html.
• “Protesters’ Rights.” American Civil Liberties Union: Know Your Rights, https://www.aclu.org/know-your-rights/protesters-rights/.g