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January 09, 2023

The Domestic Role of the United States Military

By: Stephen Dycus


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The domestic use of troops has been a fact of life and a matter of controversy at least since President Washington called out the militia to put down the Whiskey Rebellion in 1794. See William C. Banks & Stephen Dycus, Soldiers on the Home Front: The Domestic Role of the American Military (2016). In 1972, the Supreme Court noted “a traditional and strong resistance of Americans to any military intrusion into civilian affairs. That tradition has deep roots in our history.” Laird v. Tatum, 408 U.S. 1, 15 (1972). But while this tradition has generally been respected since the nation’s founding, events during the 2017-2021 administration of President Donald Trump raised questions about its depth and durability in the future.

The Posse Comitatus Act and Its Exceptions

The American tradition of avoiding the use of the military to enforce civilian laws is enshrined in the Posse Comitatus Act of 1878 (PCA), which provides:

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. 18 U.S.C. §1385.

The PCA has been interpreted by courts to prohibit the “direct, active” use of troops for law enforcement, United States v. Red Feather, 392 F. Supp. 916, 923 (D.S.D. 1975), and to bar such use if it is “regulatory, proscriptive, or compulsory.” Bissonette v. Haig, 776 F.2d 1384, 1390 (8th Cir. 1986). But the precise meanings of these limitations are subject to fact-specific, case-by-case analysis.

National Guard forces are presumed not to be bound by the PCA unless and until they are ordered to active Federal duty. See, e.g., United States v. Gilbert, 165 F.3d 470 (6th Cir. 1999). Under the command of their state or territorial governor, Guard troops can be used for law enforcement, respond to natural disasters, and perform other duties. They remain under state command even when performing federal missions “at the request of the President or Secretary of Defense” in “Title 32” status. 32 U.S.C. §502(f)(2)(A).But when called to federal service with the President as their Commander in Chief, Guard personnel operate in federal “Title 10” status and are subject to the PCA. Editor’s Note: “National Guard” encompasses the Army National Guard and the Air National Guard but not any service’s Reserve forces. 32 U.S.C. §101(3). This article does not address the status or status limitations of Reserve forces.

Guard personnel may be federalized in “time of war or of national emergency declared by Congress,” 10 U.S.C. §12301(a); at other times for up to 15 days or with the consent of Guard personnel if their governor approves, 10 U.S.C. §12301(b), (d); in other circumstances as Ready Reservists or Selected Reservists, 10 U.S.C. §§12302, 12303; when

(1) the United States, or any of the Commonwealths or possessions, is invaded or is in danger of invasion by a foreign nation;

(2) there is a rebellion or danger of a rebellion against the authority of the Government of the United States; or

(3) the President is unable with the regular forces to execute the laws of the United States, 10 U.S.C. §12406;

or pursuant to the Insurrection Act, 10 U.S.C. §§251-255.

Dating in part from 1792, the Insurrection Act provides that the President may deploy active-duty troops or federalized National Guard forces when

(a) the legislature or governor of any state asks for help in suppressing an insurrection against its government, 10 U.S.C. §251;

(b) “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,” 10 U.S.C. §252; or

(c) the President considers it “necessary to suppress, in a State, any insurrection, domestic violence, unlawful combination, or conspiracy” (1) when the “the constituted authorities of that State are unable, fail, or refuse to protect” people’s constitutional rights, or (2) if such activity “opposes or obstructs the execution of the laws of the United States or impedes the course of justice under those laws.” 10 U.S.C. §253.

Political accountability is assured by a requirement that, when “the President considers it necessary to [so] use the … armed forces,” the President must “immediately order the insurgents to disperse,” in effect, read them the riot act. 10 U.S.C. §254.

Other statutory exceptions to the PCA permit the military to share with law enforcement information collected “during the normal course of military training or operations,” 10 U.S.C. §271; operate equipment to intercept vessels or aircraft for law enforcement purposes, 10 U.S.C. §274; and detect and monitor aerial and maritime smuggling of illicit drugs, 10 U.S.C. §124. However, the law generally bars “direct assistance” by the military to civilian law enforcement, including for search and seizure, arrest, surveillance, evidence collection, and the use of force. 10 U.S.C. §275.The military may also assist the Secret Service in the performance of its protective duties. H.R.J. Res. 1292, Pub. L. No. 90-331, 82 Stat. 170 (1968). And the Stafford Act permits military assistance to civil authorities in a major disaster or emergency. 42 U.S.C. §§5170a, 5192.

Department of Defense (DOD) rules provide that, in limited circumstances, U.S. military forces, whether in federal Title 10 or state Title 32 status, may act domestically when civilian authorities cannot or will not do so. See Lawrence Kapp, Defense Primer: Defense Support of Civil Authorities (Cong. Res. Serv. IF11324), Jan. 27, 2022. For example, they may be used in a domestic crisis upon “a request for DoD assistance from civil authorities or qualifying entities or [when] authorized by the President or Secretary of Defense.” DOD Dir. No. 3025.18, Defense Support of Civil Authorities (DSCA) ¶4.c (Dec. 29, 2010, with Change 2 Mar. 19, 2018). Furthermore, military commanders may independently exercise “Emergency Authority” in order “to engage temporarily in activities that are necessary to quell large-scale, unexpected civil disturbances.” Id. at ¶4.k

The military is necessarily in charge when martial law is declared. See Joseph Nunn, Brennan Center, Martial Law in the United States: Its Meaning, Its History, and Why the President Can’t Declare It, Aug. 20, 2020. According to the Supreme Court in Ex parte Milligan, 71 U.S. (4 Wall.) 2, 127 (1866), martial law may be declared only in the event of an actual “foreign invasion or civil war” that “effectually closes the courts and deposes the civil administration.” Moreover, the Court wrote, “[a]s necessity creates the rule, so it limits its duration.” Id.

The Domestic Use of the U.S. Military During the Trump Administration

With notable exceptions, see Banks & Dycus, supra, at 166-196, active-duty military and federalized National Guard troops have seldom been deployed inside the United States except in response to natural disasters. But actual and proposed domestic uses of the military during the administration of President Trump raised questions about the legal authority and scope of such deployments.

On the Southern Border

Beginning in 2006, President George Bush and later President Barack Obama sent several thousand Guard personnel to the U.S.-Mexico border in state Title 32 status under the command of their respective governors to help curtail drug smuggling and illegal immigration. Nat’l Guard, Operation Jump Start (n.d.); Jim Greenhill, National Guard Bureau, National Guard Troops to Deploy to Southwest Border, June 24, 2010. In early 2018, President Trump ordered the Secretary of Defense to request the deployment to the U.S.-Mexico border of National Guard troops, again in state Title 32 status, to help “stop the flow of deadly drugs and other contraband, gang members and other criminals, and illegal aliens.” Presidential Memorandum for the Sec. of Defense, the Att’y General, and the Sec. of Homeland Security, Securing the Southern Border of the United States (Apr. 4, 2018). More than 4,000 Guard personnel from 20 states were deployed there. Davis Winkie, Death, Drugs and a Disbanded Unit: How the Guard’s Mexico Border Mission Fell Apart, Army Times, Dec. 8, 2021. President Biden revoked the order three years later. Exec. Order No. 14,010, Creating a Comprehensive Regional Framework to Address the Causes of Migration, to Manage Migration Throughout North and Central America, and to Provide Safe and Orderly Processing of Asylum Seekers at the United States Border, 86 Fed. Reg. 8267 (Feb. 2, 2021).

Later in 2018, President Trump began sending nearly 6,000 active-duty servicemembers to the border to help stanch the flow of migrants, authorizing the forces to perform “military protective activities,” including “a show or use of force (including lethal force, where necessary), crowd control, temporary detention, and cursory search” to protect border agents. Memorandum for the President, Department of Defense Support for Border Security (Nov. 20, 2018). These forces did “not appear to have a direct legislative mandate to protect or patrol the border or to engage in immigration enforcement.” Jennifer K. Elsea, The President’s Authority to Use the National Guard or the Armed Forces to Secure the Border 3 (Cong. Res. Serv. LSB10121), Apr. 19, 2018. See also William Banks, Legal Analysis of “Cabinet Memo” on the Military’s Role at Southern Border, Just Security, Nov. 26, 2018; Joseph Nunn, DOD Inspector General’s Report Whitewashes Potential Violations of the Posse Comitatus Act, Just Security, Sept. 3, 2020 (calling the authorized “use of force” unsupported by any statutory exception to the PCA). They were used mainly for stringing concertina wire, transporting Immigration and Customs Enforcement personnel, conducting surveillance, and caring for Border Patrol horses. Military Support for Customs and Border Protection Along the Southern Border Under the Posse Comitatus Act, 45 Op. O.L.C. ___ (Jan. 19, 2021).

In February 2019, President Trump declared a national emergency at the southern border, authorizing the call-up of military personnel and specifically relying on the authority of 10 U.S.C. §2808(a) for them to “undertake military construction projects.” Proc. No. 9844, Declaring a National Emergency Concerning the Southern Border of the United States, 84 Fed. Reg. 4949 (Feb. 15, 2019). President Biden revoked the emergency declaration two years later. Proc. No. 10,142, Termination of Emergency With Respect to the Southern Border of the United States and Redirection of Funds Diverted to Border Wall Construction, 86 Fed. Reg. 7467 (Jan. 20, 2021). But, in 2021, President Biden’s Defense Secretary, Lloyd Austin, approved the continued deployment until September 2022 of as many as 3,000 active-duty and National Guard personnel on the southern border. Rose L. Thayer, Deployment of US Troops Along US-Mexico Border Will Stretch into a Fourth Year, Pentagon Announces, Stars & Stripes, July 6, 2021.

For Civil Unrest

The Insurrection Act was last invoked in 1992 when President George H.W. Bush authorized the deployment of active-duty and Guard forces “to restore law and order” in Los Angeles after the acquittal of police officers charged with beating Rodney King. Exec. Order No. 12,804, Providing for the Restoration of Law and Order in the City and County of Los Angeles, and Other Districts of California, 57 Fed. Reg. 19,361 (May 1, 1992). The Act was not invoked when protests broke out around the country following the killing of George Floyd by Minneapolis police on May 25, 2020. Incidents of violence were contained by local and state authorities, sometimes aided by National Guard troops under the command of their governor. Nevertheless, in an address from the White House Rose Garden on June 1, 2020, President Trump announced,

I have strongly recommended to every governor to deploy the National Guard in sufficient numbers that we dominate the streets.... If a city or a state refuses to take the actions that are necessary to defend the life and property of their residents, then I will deploy the United States military and quickly solve the problem for them. Statement by the President, June 1, 2020.

While the President spoke, the D.C. National Guard helped law enforcement forcefully clear peaceful protestors, clergy, and media from in and around Lafayette Square. That enabled President Trump, accompanied by Defense Secretary Mark Esper, Chairman of the Joint Chiefs of Staff General Mark Milley, and other senior government officials, to walk from the Rose Garden to St. John’s Church so that the President could be photographed there. Peter Baker et al., How Trump’s Idea for a Photo Op Led to Havoc in a Park, N.Y. Times, June 2, 2020.

Earlier the same day, White House officials reportedly drafted a proclamation to invoke the Insurrection Act and deploy active-duty troops in Washington, D.C. But upon the advice of Attorney General William Barr, Secretary Esper, and General Milley, President Trump decided not to issue the proclamation. Michael S. Schmidt & Maggie Haberman, Trump Weighed Insurrection Act Amid Protests, N.Y. Times, June 26, 2021. See also Scott R. Anderson & Michel Paradis, Can Trump Use the Insurrection Act to Deploy Troops to American Streets?, Lawfare, June 3, 2020 (expressing doubt that criteria for invoking the Insurrection Act were met). He did, however, approve placing 1,600 active-duty personnel on standby outside D.C. and deploying about 5,000 National Guard personnel from 11 states in Title 32 status inside D.C. for several days. Aaron C. Davis, How Trump Amassed a Red-State Army in the Nation’s Capital — and Could Do So Again, Wash. Post, Oct. 1, 2020. See also Steve Vladeck, Why Were Out-of-State National Guard Units in Washington, D.C.? The Justice Department’s Troubling Explanation, Lawfare, June 9, 2020 (questioning the legality of the Guard deployment).

In Elections

In the run-up to the November 2020 presidential election, there was concern about possible violence at polling places. But while governors in a number of states activated National Guard troops to help maintain order, only a few minor disruptions were reported. Gina Harkins & Matthew Cox, Here’s What National Guard Units Across the Country Will Be Doing on Election Day,, Oct. 31, 2020; Zolan Kanno-Youngs, Jennifer Steinhauer & Nicole Perlroth, Despite Fears of Violence, Election Day Proceeds Smoothly as Millions Line Up to Vote, N.Y. Times, Nov. 3, 2020.

There was also concern that President Trump might cite threats or isolated acts of violence as a pretext to send military forces to polling places. Jennifer Steinhauer & Helene Cooper, At Pentagon, Fears Grow That Trump Will Pull Military into Election Unrest, N.Y. Times, Sept. 25, 2020; Robert S. Taylor, Contingency Planning for Presidential Interference with the Election, Lawfare, Aug. 4, 2020. After the election, President Trump apparently considered but rejected an executive order that called for the Secretary of Defense to “seize, collect, retain and analyze all [voting] machines, equipment, electronically stored information, and material records.” Betsy Woodruff Swan, Read the Never-Issued Trump Order that Would Have Seized Voting Machines, Politico, Jan. 21, 2022; Alan Feuer et al., Trump Had Role in Weighing Proposals to Seize Voting Machines, N.Y. Times, Jan. 31, 2022. Nonetheless, General Milley declared that, “if there’s a disputed election, that’ll be handled by Congress and the courts. There’s no role for the U.S. military in determining the outcome of a U.S. election. Zero, there is no role there.” Missy Ryan, As Election Nears, Pentagon Leaders’ Goal of Staying Out of Elections Is Tested, Wash. Post, Oct. 14, 2020

At least three provisions of the U.S. Code support General Milley’s declaration. One bars military personnel from deployment anywhere an election is being held “unless such force be necessary to repel armed enemies of the United States.” 18 U.S.C §592. A second prohibits members of the armed forces from, inter alia, preventing “by force, threat, intimidation, advice or otherwise any qualified voter of any State from fully exercising the right of suffrage,” or from interfering with election officials. 18 U.S.C §593. A third forbids anyone, military or civilian, from intimidating voters for the purpose of interfering with or affecting the content of their vote. 18 U.S.C. §594. Defense Department rules also forbid the deployment of active-duty forces or Title 32 Guard personnel at polling places. DOD Dir. No. 3025.18, supra, at ¶4.t. Ultimately, no federal military forces were deployed on Election Day.

To Protect Congress and the U.S. Capitol

On January 6, 2021, when Congress convened to certify the votes of the Electoral College, President Trump’s supporters stormed the U.S. Capitol Building, forced Congress to adjourn, threatened the Vice President and members of Congress, and did extensive damage. Capitol and D.C. police were completely overwhelmed.

At 1:49 p.m., minutes before the rioters breached the Capitol, the Capitol Police chief requested the immediate assistance of the D.C. National Guard. Unlike a state’s Guard units, which are commanded by the governor unless called to federal service, the D.C. Guard is always under the command of the President. D.C. Code §49-409. The D.C. Guard did not receive the requisite approval for deployment from Acting Defense Secretary Christopher Miller and Secretary of the Army Ryan McCarthy until 5:08 p.m. When Guard troops finally arrived at the Capitol, the rioters had already begun to disperse. Kate Brannen & Ryan Goodman, The Official and Unofficial Timeline of Defense Department Actions on January 6, Just Security, May 11, 2021. It is not clear whether or to what extent President Trump was involved in the decision to deploy the D.C. Guard. See Ryan Goodman & Justin Hendrix, Crisis of Command: The Pentagon, The President, and January 6, Just Security, Dec. 21, 2021 (detailing political concerns leading up to and including the January 6 attack on the Capitol); Staffs of S. Comms. on Homeland Security & Gov’t Aff. and Rules & Admin., 117th Cong., Examining the U.S. Capitol Attack: A Review of the Security, Planning, and Response Failures on January 6 (June 8, 2021), at 62-95 (describing confusion, bureaucracy, and concerns about “optics” in deploying the Guard).

In the aftermath of the attack, Secretary Miller authorized the mobilization of several thousand National Guard troops from six states to preserve order in and around the Capitol and “help secure the peaceful transfer of power to President-elect Joseph Biden on Jan. 20.” Jim Garamone, DOD Details National Guard Response to Capitol Attack, DOD News, Jan. 8, 2021. Thousands of additional Guard personnel were deployed for the inauguration. Zolan Kanno-Youngs & Helene Cooper, Troops Flood a Rattled Washington Ahead of the Biden Inauguration, N.Y. Times, Jan. 20, 2021. See DOD Instr. No. 3025.20, Defense Support of Special Events (Apr. 6, 2012, with Change 1, May 24, 2017), at Encl. 3, ¶2.b(3)(d). The last Guard troops did not leave the District until May. Amanda Macias, National Guard Troops Leave Capitol Months After Deadly Jan. 6 Insurrection, CNBC, May 24, 2021.

The Domestic Use of the U.S. Military in the Future

More than 225 years of experience have answered some questions about the use of U.S. military forces in America. Other questions remain unanswered or incompletely answered.

Criteria for invoking the Insurrection Act are not nearly clear enough. The President has broad discretion to order federal or federalized military forces to suppress any “insurrection, domestic violence, unlawful combination, or conspiracy, if it . . . opposes or obstructs the execution of the laws of the United States or impedes the course of justice under those laws.” 10 U.S.C. §253. The President may need this flexibility to combat domestic terrorism. However, the current, broad language might enable a president to deploy military forces even without any objective assessment of actual need. See Mark Nevitt, Good Governance Paper No. 6 (Part One): Domestic Military Operations — Reforming the Insurrection Act, Just Security, Oct. 20, 2020; Mark Nevitt, Good Governance Paper No. 6 (Part Two): Domestic Military Operations — The Role of the National Guard, Posse Comitatus Act and More, Just Security, Oct. 21, 2020. The Insurrection Act is also unclear as to its applicability to the D.C. Guard and to Guard forces deployed to the District. As currently written, the Act refers only to the deployment of “state” militias within “states.” This lack of certainty could be resolved either by admitting the District of Columbia to statehood or by amending 10 U.S.C. §255 to define the District as a state for purposes of the Insurrection Act.

Rules for the use of National Guard personnel in state Title 32 status also need clarification. DOD regulations stipulate that Title 32 Guard forces are not barred from direct, active law enforcement duties, DOD Instr. No. 3025.21, Defense Support of Civilian Law Enforcement Agencies 18-19 (Feb. 27, 2013, with Change 1 Feb. 8, 2019), at 2, even though they are conducting a federal mission. And they are not considered bound by the Posse Comitatus Act because they remain under state command. But in June 2020, Title 32 Guard personnel from 11 states deployed to the District of Columbia “were in fact reporting up through the D.C. Guard’s chain of command to the president.” Cole Blum & Soren Dayton, The National Guard at Lafayette Square and the January 6th Attempted Insurrection: Fixes for the FY2022 NDAA, Just Security, Aug. 31, 2021. In addition to confusion about command authority, a similar situation in the future could result in one state’s Guard forces being deployed to another state without either the consent of the receiving state or the political accountability that would accompany those forces being federalized under the Insurrection Act. Joseph Nunn, Brennan Ctr. for Justice, The Posse Comitatus Act Explained, Oct. 14, 2021; Nevitt, Good Governance Paper No. 6 (Part Two), supra.

In the matter of federal versus state status, the D.C. National Guard is of particular concern. See generally Lawrence Kapp, Alan Ott & Michael A. Foster, National Guard Civil Support in the District of Columbia (Cong. Res. Serv. IF11768), Feb. 23, 2021. Because the President is the commander in chief of the D.C. Guard, the D.C. mayor not only lacks the authority to mobilize and deploy the D.C. Guard but also has no ability to limit or control the deployment of state Guard forces in the District. See Elizabeth Goitein & Joseph Nunn, Why D.C.’s Mayor Should Have Authority Over the D.C. National Guard, Just Security, Jan. 8, 2021. The District of Columbia National Guard Home Rule Act, H.R. 657, 117th Cong. (2021), would make the D.C. mayor the commander-in-chief of the D.C. National Guard and shift Guard authorities from the President to the Mayor.

There are no perfect solutions to the issues presented here. But it is clear that the nation’s future security depends in substantial part on the continued commitment of our leaders to the rule of law and to the tradition of avoiding unnecessary military entanglement in civilian affairs.

Stephen Dycus

Professor Emeritus, Vermont Law School

Stephen Dycus is Professor Emeritus at Vermont Law School. He is co-author of the Aspen casebooks National Security Law (7th ed. 2020) and Counterterrorism Law (4th ed. 2020). He was also founding Co-Editor-in-Chief of the Journal of National Security Law & Policy and founding Chair of the National Security Law Section of the Association of American Law Schools. Dycus previously served on the Advisory Committee of the ABA Standing Committee on Law and National Security.

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The views expressed herein represent the opinions of the authors. They have not been approved by the House of Delegates or the Board of Governors of the American Bar Association and, accordingly, should not be construed as representing the position of the Association or any of its entities. Nothing contained in this publication is to be considered as the rendering of legal advice for specific cases, and readers are responsible for obtaining such advice from their own legal counsel. This publication is intended for educational and informational purposes only.

The material in all ABA publications is copyrighted and may be reprinted by permission only. Request reprint permission here.