Posse Comitatus Act

Editorial Note

The situation in Los Angeles has deteriorated and there are a lot of opinions on the matter. Protests in and around Los Angeles began on Friday after federal immigration agents arrested at least 44 people. The arrests come amid Trump's crackdown on immigration. President Trump called in the U.S. National Guard and Marines. The President using the National Guard is a serious matter but not unprecedented. There are questions swirling about whether the President has authority to send the National Guard.  

Executive Summary

The Posse Comitatus Act of 1878 prohibits the willful use of the U.S. Army or Air Force to enforce domestic laws unless authorized by the Constitution or an act of Congress. This principle reflects longstanding American discomfort with military involvement in civilian matters. While Congress and the President have authorized certain exceptions, including under the Insurrection Act, federal military power is generally restricted from direct law enforcement roles. Over time, Congress has also permitted specific support roles, such as information-sharing and logistics aid, particularly in cases involving terrorism or drug interdiction. Despite this framework, the line between military and civilian law enforcement remains a subject of legal and constitutional debate.

Key Provisions

• Historical and Constitutional Foundations (pg. 1-3, paras. 1-4)

• The U.S. Constitution authorizes Congress to use militias to execute laws, suppress insurrections, and repel invasions. It also mandates protection for states against domestic violence upon request.
• These powers are mirrored in the Insurrection Acts, which have been used in various historical crises.
• The Founding Fathers were influenced by English traditions, especially the Petition of Right (1628), which limited martial law in peacetime.
• The U.S. has a tradition, rooted in the Magna Carta and reinforced by colonial experience, that resists military involvement in civilian legal matters. Footnote 7: Magna Carta, ch. 29 (1215); Footnote 12: Petition of Right (1628).

• The Posse Comitatus Act (18 U.S.C. § 1385) (pg. 4, para. 1)

• This law prohibits using the Army or Air Force to enforce domestic laws unless expressly permitted by the Constitution or Congress.
• The law is primarily enforced through military self-restraint rather than prosecutions.
• It does not mention the Navy or Marine Corps, but administrative rules apply the same restriction to them.
• The Coast Guard, as a law enforcement agency, is excluded from these restrictions by separate statutory authority.

• Exceptions to the Posse Comitatus Act (pg. 4-5, paras. 2-3)

• Statutory exceptions include:
• The Insurrection Acts (10 U.S.C. §§ 251-255), which allow the President to deploy military forces to suppress insurrections or enforce federal authority.
• Support provisions (10 U.S.C. §§ 271-284), which permit assistance in the form of intelligence, equipment, or logistics.
• By creating narrowly focused statutes authorizing assistance in specific cases, such as laws permitting Defense Department support to law enforcement in cases of terrorism or biological weapons threats. Footnotes 341–344.
• Courts have held that violations occur when:
1. Military investigators are actively used by law enforcement.
2. Military activity dominates civilian operations.
3. Military power imposes regulatory or compulsory authority on civilians. Footnote 1: United States v. Red Feather, 392 F. Supp. 916 (D.S.D. 1975).

• Use of Troops in Domestic Crises - Legal Thresholds (pg. 6-12)

• Federal troops have been historically deployed during events like the Whiskey Rebellion (1794), anti-tax protests, civil rights struggles, and major labor strikes.
• Presidential authority to send troops hinges on statutory and constitutional provisions requiring evidence of rebellion, obstruction, or inability of civil authorities to maintain order.
• Presidents must issue a proclamation ordering persons involved to disperse before deploying troops under the Insurrection Acts. Footnote 42: 10 U.S.C. § 254.

• Federal Aid at State Request (10 U.S.C. § 251) (pg. 13-14, paras. 1-2)

• Governors may request federal troops when domestic violence overwhelms state resources.
• The President retains command of the troops and decides whether to act.
• This has been invoked for events like civil unrest in Detroit (1967) and Los Angeles riots (1992).

• Enforcing Federal Law Without State Request (10 U.S.C. § 252) (pg. 14-15, paras. 1-3)

• The President can deploy troops if law enforcement is blocked or impracticable. Under 10 U.S.C. § 252, the President may deploy the Armed Forces when unlawful obstructions, combinations, or rebellions prevent the execution of federal law and civil authorities are unable to manage the situation. This action does not require a request or approval from state officials. Footnote 279: Based on Article I, Section 8, Clause 15 of the Constitution.
• This authority was first invoked after the Posse Comitatus Act during the 1878 lawlessness in New Mexico Territory, where armed bands threatened court operations and public order. Once a presidential proclamation was issued, federal troops restored order. Footnote 280.
• Presidential intervention in such cases often followed a formal proclamation ordering those obstructing the law to disperse, as required under 10 U.S.C. § 254. Footnote 254.
• In Chicago, 1894, during the violent Pullman railroad strike, President Cleveland sent troops without the Illinois governor’s request. Troops acted after marshals and U.S. attorneys reported local law enforcement’s inability to enforce federal court orders and protect mail routes. Footnotes 286–289.
• The provision has also been used in:
• Utah (1885) to enforce anti-polygamy laws. Footnote 292.
• Washington State (1886–1887) during anti-Chinese riots. Footnotes 293–294.
• Arkansas (1914) to secure courts and federal property during civil unrest. Footnote 296.
• Wounded Knee (1973) where federal law enforcement received significant military support—although troops were not formally deployed under § 252, the event raised concerns about unauthorized military involvement. Footnote 304.
• Additional uses include:
• Protecting the Pentagon during anti-war protests (1967), though ultimately justified under inherent executive authority to protect federal property rather than under § 252. Footnote 300.
• Postal strike (1970)—National Guard units were federalized to continue mail delivery. Footnote 301.
• Federal penitentiary riot in Atlanta (1987)—President Reagan issued a proclamation and prepared troops, though the crisis ended before deployment. Footnote 307.
• These instances illustrate that presidential authority under § 252 is designed for emergencies where federal law or functions are at risk and where state officials either cannot or will not act effectively.

• Protection of Civil Rights (10 U.S.C. § 253) (pg. 15, para. 2)

• Troops may be used without state consent if civil rights are being denied and local authorities cannot or will not act.
• Invoked during school desegregation (e.g., Little Rock, AR, 1957) and civil rights marches (e.g., Selma, AL, 1965). Footnote 310: Exec. Order No. 10730 (1957).

• Constitutional Questions (pg. 18-20)

• Some scholars and court opinions suggest a broader constitutional principle against martial law or military enforcement of civil law.
• Courts have generally avoided ruling that the Posse Comitatus Act enshrines constitutional prohibitions, preferring statutory interpretations.
• The Constitution allows Congress to regulate the militia and military use in domestic contexts, but also grants the President considerable latitude as Commander in Chief. Footnote 193: U.S. Const. art. I, § 8, cl. 15

Source: https://www.congress.gov/crs-product/R42659?q=%7B%22search%22%3A%22insurrection+act%22%7D&s=1&r=3&overview=open#content