Posse Comitatus Act
Great Seal of the United States
Other short titles
  • Knott Amendment
  • Posse Comitatus Act of 1878
Long titleAn act making appropriations for the support of the Army for the fiscal year ending June thirtieth, eighteen hundred and seventy-nine, and for other purposes.
NicknamesArmy Appropriations Act of 1878
Enacted bythe 45th United States Congress
EffectiveJune 18, 1878
Public lawPub. L.Tooltip Public Law (United States) 45–263
Statutes at Large20 Stat. 145 aka 20 Stat. 152
U.S.C. sections created18 U.S.C. § 1385
Legislative history
  • Introduced in the House as H.R. 4867 by Herman L. Humphrey (R-WI), William Kimmel (D-MD) on May 13, 1878
  • Passed the House on May 18, 1878 (130–117)
  • Passed the Senate on June 6, 1878 (36–23)
  • Reported by the joint conference committee on June 15, 1878; agreed to by the House on June 15, 1878 (154–58) and by the Senate on June 15, 1878 (Agreed)
  • Signed into law by President Rutherford B. Hayes on June 18, 1878
Major amendments
1956, 1981, 2021

The Posse Comitatus Act is a United States federal law (18 U.S.C. § 1385, original at 20 Stat. 152) signed on June 18, 1878, by President Rutherford B. Hayes which limits the powers of the federal government in the use of federal military personnel to enforce domestic policies within the United States. Congress passed the Act as an amendment to an army appropriation bill following the end of Reconstruction and updated it in 1956, 1981 and 2021.

The Act originally applied only to the United States Army, but a subsequent amendment in 1956 expanded its scope to the United States Air Force. In 2021, the National Defense Authorization Act for Fiscal Year 2022 further expanded the scope of the Act to cover the United States Navy, Marine Corps, and Space Force. The Act does not prevent the Army National Guard or the Air National Guard under state authority from acting in a law enforcement capacity within its home state or in an adjacent state if invited by that state's governor. The United States Coast Guard (under the Department of Homeland Security) is not covered by the Act either, primarily because although it is an armed service, it also has a maritime law enforcement mission.

The title of the Act comes from the legal concept of posse comitatus, the authority under which a county sheriff, or another law officer, can conscript any able-bodied person to assist in keeping the peace.


The Act, § 15 of the appropriations bill for the Army for 1879 (found at 20 Stat. 152) was a response to, and subsequent prohibition of, the military occupation of the former Confederate States by the United States Army during the twelve years of Reconstruction (1865–1877) following the American Civil War (1861–1865).

The U.S. Constitution places primary responsibility for the holding of elections in the hands of the individual states. The maintenance of peace, conduct of orderly elections, and prosecution of unlawful actions are all state responsibilities, according to any state's role of exercising police power and maintaining law and order, whether part of a wider federation or a unitary state.[1] However, in the former Confederate States, many paramilitary groups sought to suppress, often through intimidation and violence, African-American political power and return the South to rule by the predominantly white Democratic Party. Although African Americans were initially supported by the federal government, as Reconstruction went on, that support waned.[2] Following the bitterly disputed 1876 U.S. presidential election and Compromise of 1877, Congressmen and Senators from the former Confederate States returned to Washington and prioritized prohibiting the federal government from reimposing control over their states.[3] After President Hayes used federal troops to end the Great Railroad Strike of 1877, there was sufficient bipartisan support to pass what became the Posse Comitatus Act.[4][5][3]

The original Posse Comitatus Act referred exclusively to the United States Army. The Air Force, established during the 20th century initially as a branch of the Army, was added in 1956. The Navy and Marine Corps were not mentioned in the Act but were subject to the same restrictions by Department of Defense regulation until their inclusion in the act in 2021.[3][6] The Space Force, established in 2020, was also included in the Act in 2021. The United States Coast Guard is not included in the act even though it is part of the six armed services as it is explicitly given federal law enforcement authority on maritime law.[7] The modern Coast Guard did not exist at the time the Act became law in 1878. Its predecessor, the United States Revenue Cutter Service, was primarily a customs enforcement agency and part of the United States Department of the Treasury.[8] In 1915, when the Revenue Cutter Service and the United States Lifesaving Service were amalgamated to form the Coast Guard, the service was both made a military branch and given federal law enforcement authority.

In the mid-20th century, the administration of President Dwight D. Eisenhower used an exception to the Posse Comitatus Act, derived from the Enforcement Acts, to send federal troops into Little Rock, Arkansas, during the 1957 school desegregation crisis. The Arkansas governor had opposed desegregation after the United States Supreme Court ruled in 1954 in the Brown v. Board of Education that segregated public schools were unconstitutional. The Enforcement Acts, among other powers, allowed the president to call up military forces when state authorities were either unable or unwilling to suppress violence that was in opposition to the citizens' constitutional rights.[9]

In the summer of 2020, the George Floyd protests in Washington, D.C. generated controversy when National Guard troops were called in to suppress protests without President Donald Trump's invoking the Insurrection Act (though he threatened to do so). One set of troops, the District of Columbia National Guard, has historically operated as the equivalent of a state militia (under Title 32 of the United States Code) not subject to Posse Comitatus Act restrictions, even though it is a federal entity under the command of the President and the Secretary of the Army.[10] National Guard troops from cooperative states were also called in at the request of federal agencies, some of whom were deputized as police.[11] Attorney General William Barr cited 32 U.S.C. § 502(f)(2)(a),[11] which says National Guard troops may engage in "support of operations or missions undertaken by the member's unit at the request of the President or Secretary of Defense." Saying the intent of §502 (titled "Required drills and field exercises") was to cover training exercises only, Senator Tom Udall and U.S. Representative Jim McGovern described this as a "loophole" to circumvent Posse Comitatus Act restrictions, and introduced legislation to close it.[12]

In 2020, U.S. Representative Adam Schiff introduced an amendment to the Act to expand its coverage to include the U.S. Navy, Marine Corps, and Space Force.[13] This amendment was eventually included in the 2022 National Defense Authorization Act.[14]


The original provision was enacted as Section 15 of chapter 263, of the Acts of the 2nd session of the 45th Congress.

Sec. 15. From and after the passage of this act 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; and no money appropriated by this act shall be used to pay any of the expenses incurred in the employment of any troops in violation of this section and any person willfully violating the provisions of this section shall be deemed guilty of a misdemeanor and on conviction thereof shall be punished by fine not exceeding ten thousand dollars or imprisonment not exceeding two years or by both such fine and imprisonment.[15]

The text of the relevant legislation is as follows:

18 U.S.C. § 1385. Use of Army, Navy, Marine Corps, Air Force, and Space Force as posse comitatus: Whoever, except in cases and under circumstances expressly authorized by the Constitution or Act of Congress, willfully uses any part of the Army, the Navy, the Marine Corps, the Air Force, or the Space Force as a posse comitatus or otherwise to execute the laws shall be fined under this title or imprisoned not more than two years, or both.

Also notable is the following provision within Title 10 of the United States Code (which concerns generally the organization and regulation of the armed forces and Department of Defense):

10 U.S.C. § 275. Restriction on direct participation by military personnel The Secretary of Defense shall prescribe such regulations as may be necessary to ensure that any activity (including the provision of any equipment or facility or the assignment or detail of any personnel) under this chapter does not include or permit direct participation by a member of the Army, Navy, Air Force, or Marine Corps in a search, seizure, arrest, or other similar activity unless participation in such activity by such member is otherwise authorized by law.

2006–2007 suspension

In 2006, Congress modified the Insurrection Act as part of the 2007 Defense Authorization Bill (repealed as of 2008). On September 26, 2006, President George W. Bush urged Congress to consider revising federal laws so that U.S. armed forces could restore public order and enforce laws in the aftermath of a natural disaster, terrorist attack or incident, or other condition. These changes were included in the John Warner National Defense Authorization Act for Fiscal Year 2007 (H.R. 5122), which was signed into law on October 17, 2006.[16]

Section 1076 is titled "Use of the Armed Forces in major public emergencies". It provided that:

The President may employ the armed forces ... to ... restore public order and enforce the laws of the United States when, as a result of a natural disaster, epidemic, or other serious public health emergency, terrorist attack or incident, or other condition ... the President determines that ... domestic violence has occurred to such an extent that the constituted authorities of the State or possession are incapable of maintaining public order ... or [to] suppress, in a State, any insurrection, domestic violence, unlawful combination, or conspiracy if such ... a condition ... so hinders the execution of the laws ... that any part or class of its people is deprived of a right, privilege, immunity, or protection named in the Constitution and secured by law ... or opposes or obstructs the execution of the laws of the United States or impedes the course of justice under those laws.[17]

In 2008, these changes in the Insurrection Act of 1807 were repealed in their entirety, reverting to the previous wording of the Insurrection Act.[18] It was initially written to limit presidential power as much as possible in the event of insurrection, rebellion, or lawlessness.

Exclusions and limitations

There are several situations in which the Act does not apply. These include:

Exclusion applicable to U.S. Coast Guard

See also: Missions of the United States Coast Guard

Although it is an armed service,[21] the U.S. Coast Guard, which operates under the United States Department of Homeland Security during peacetime, is not restricted by the Posse Comitatus Act but has explicit authority to enforce federal law. This is true even when the Coast Guard operates as a service within the United States Navy during wartime.[8]

In December 1981, the Military Cooperation with Civilian Law Enforcement Agencies Act was enacted, clarifying permissible military assistance to domestic law enforcement agencies and the Coast Guard, especially in combating drug smuggling into the United States. Posse Comitatus clarifications emphasize supportive and technical assistance (such as the use of facilities, vessels, and aircraft, as well as intelligence support, technological aid, and surveillance) while generally prohibiting direct participation of U.S. military personnel in law enforcement (such as search, seizure, and arrests). For example, a U.S. Navy vessel may be used to track, follow, and stop a vessel suspected of drug smuggling, but Coast Guard Law Enforcement Detachments (LEDETs) embarked aboard the Navy vessel would perform the actual boarding and, if needed, arrest the suspect vessel's crew.[8]

Advisory and support roles

Federal troops have a long history of domestic roles, including occupying secessionist Southern states during Reconstruction and putting down major urban riots. The Posse Comitatus Act prohibits using active duty personnel to "execute the laws"; however, there is disagreement over whether this language may apply to troops used in an advisory, support, disaster response, or other homeland defense role, as opposed to domestic law enforcement.[1]

On March 10, 2009, members of the U.S. Army Military Police Corps from Fort Rucker were deployed to Samson, Alabama, in response to a shooting spree. Samson officials confirmed that the soldiers assisted in traffic control and securing the crime scene. The governor of Alabama did not request military assistance, nor did President Barack Obama authorize their deployment. Subsequent investigation found that the Posse Comitatus Act was violated and several military members received "administrative actions".[22][23]

See also


  1. ^ a b "The Posse Comitatus Act: Setting the record straight on 124 years of mischief and misunderstanding before any more damage is done" (PDF). Military Law Review. 175. 2003 – via jagcnet.army.mil.
  2. ^ Foner, Eric (2011). Reconstruction: America's Unfinished Revolution, 1863-1877. Harper. ISBN 9780062035868.
  3. ^ a b c Elsea, Jennifer K. (November 6, 2018). "The Posse Comitatus Act and Related Matters: The Use of the Military to Execute Civilian Law" (PDF). fas.org. Congressional Research Service, Federation of American Scientists. Retrieved June 3, 2020.
  4. ^ "Week In Review". WBUR.org. April 6, 2018. Retrieved September 29, 2019.
  5. ^ Gronowicz, Anthony (2015). "Crushing Strikes through the U.S. Military, 1875-1915". Working USA. 18 (4): 629–648. doi:10.1111/wusa.12216.
  6. ^ Mazzetti, Mark; Johnston, David (June 22, 2009). "Bush Weighed Using Military in Arrests". The New York Times.
  7. ^ Grant, Dustin L.; Neil, Matthew J. (February 2020). "The Case for Space: A Legislative Framework for an Independent United States Space Force" (PDF). Wright Flyer Papers. pp. 22–23.
  8. ^ a b c "Coast Guard Law Enforcement Detachments (LEDETs): A History". United States Coast Guard. August 29, 2008. Archived from the original on February 12, 2010.
  9. ^ Lieberman, Jethro (1999). A Practical Companion to the Constitution: How the Supreme Court Has Ruled on Issues from Abortion to Zoning. University of California Press. ISBN 0-520-21280-0.
  10. ^ Anderson, Scott R.; Paradis, Michel (June 3, 2020). "Can Trump Use the Insurrection Act to Deploy Troops to American Streets?". lawfareblog.com. The Lawfare Institute. Retrieved March 30, 2022.
  11. ^ a b @KerriKupecDOJ (June 9, 2020). "Letter from Attorney General Barr to D.C. Mayor Muriel Bowser on the Trump Administration's restoration of law and order to the District" (Tweet). Retrieved March 30, 2022 – via Twitter. This posted online a letter from then-Attorney General William Barr
  12. ^ Udall, Tom; McGovern, Jim (August 7, 2020). "Trump and Barr used a loophole to deploy the National Guard to U.S. cities. It's time to close it". NBC News.
  13. ^ Schiff, Adam B. (June 22, 2020). "H.R.7297 - 116th Congress (2019-2020): Strengthening the Posse Comitatus Act of 2020". www.congress.gov. Retrieved April 26, 2022.
  14. ^ Scott, Rick (December 27, 2021). "S.1605 - 117th Congress (2021-2022): National Defense Authorization Act for Fiscal Year 2022". www.congress.gov. Retrieved April 26, 2022.
  15. ^ 152 Sess. lI. Ch. 263, 264. 45th Congress (1878) at Wikisource
  16. ^ "John Warner National Defense Authorization Act for Fiscal Year 2007 (2006 – H.R. 5122)". Retrieved September 29, 2019 – via GovTrack.us.
  17. ^ H.R. 5122, pp. 322–23
  18. ^ "H.R. 4986: National Defense Authorization Act for Fiscal Year 2008". 2008. Retrieved January 24, 2008 – via GovTrack.us.
  19. ^ Nofi, Albert A. (July 2007). "The Naval Militia: A Neglected Asset?" (PDF). CNA. Retrieved February 19, 2019.
  20. ^ Murphy, Jack (June 28, 2016). "That Time Delta Force Got Called in to Sort out a Georgia Prison Riot". sofrep.com. Retrieved June 12, 2020.
  21. ^ "Establishment of the Coast Guard". U.S. Code. U.S. House of Representatives. Retrieved May 28, 2023.
  22. ^ "Army reviews shows troop use in Samson killing spree violated federal law". The Birmingham News. October 19, 2009. Retrieved March 30, 2022.
  23. ^ McGinniss, Gary L. "Revolutionizing Northern Command" (PDF). dtic.mil. Archived from the original (PDF) on October 2, 2012.

Further reading