June 8th marks the one-year anniversary of President Donald Trump’s deployment of National Guard troops to Los Angeles, the first in a series of domestic troop deployments, including one that continues today in Washington, D.C. These deployments — primarily launched under the guise of fighting crime — pose a growing threat to the constitutional and legal framework that, for 250 years, has divided the roles of internal security and external defense to the mutual benefit of both.
Forcing U.S. servicemembers to police American streets isn’t just dangerous for the rule of law, it also harms the military itself. The negative and counterproductive consequences of placing military personnel on the frontlines of domestic law enforcement are well-established and remarkably consistent. Drawing on incidents from American history and contemporary examples from around the world, we detail these risks in a new report, “The Dangers of Military Intervention in Civilian Law Enforcement.”
The topline findings are clear:
When these civil-military lines blur, even well-intentioned domestic military operations can produce unintended consequences that are difficult to reverse…. These dangers — escalation, disillusionment, and politicization — are the predictable outcomes of military intervention in civilian law enforcement.
Police are trained to enforce the law and de-escalate violence, militaries, however, are tasked with deploying overwhelming force. The mismatch of tool to task that sending troops to enforce the law entails puts civilians (and troops themselves) in the crosshairs, jeopardizes military morale and readiness, and injects politics into the armed forces. Escalation, disillusionment in the ranks, and politicization are virtually inevitable when this line in the civil-military boundary is blurred. All Americans should be deeply concerned about the increased deployments of federal military personnel for domestic policing purposes.
Lessons from U.S. History
The first American century witnessed numerous domestic uprisings that challenged the legitimacy of the new government, including a civil war that posed an existential threat. Wary of concentrated central political power, the federal government for much of the nineteenth century relied on a patchwork of state militias and Regular U.S. Army troops for managing internal security — a fundamentally different reality from the modern era of robust and well-funded state and local police forces. The evolving responses to these early domestic crises shaped how federal force is understood, organized, and authorized for use.
Shays’ Rebellion in 1786 first convinced early leaders of the inadequacy of the federal government’s capacity to respond to civil unrest under the Articles of Confederation, and informed the U.S. Constitution that would replace it. Later, both Presidents George Washington and John Adams utilized statutory authorities to deploy federal military force against anti-tax uprisings — during the Whiskey and Fries Rebellions, respectively — only to later learn that these deployments cost far more than the issue originally at stake.
Former Vice President Aaron Burr’s botched plot to seize western territory prompted the passage of the Insurrection Act in 1807, which expanded the president’s authority to deploy federal military personnel in “all cases of insurrection, or obstruction to the laws … for the purpose of suppressing such insurrection, or of causing the laws to be duly executed.” The Insurrection Act remains intact today, though invocations of its authority have remained exceedingly rare since its enactment.
Even when legally authorized and fully budgeted, domestic troops deployments take a toll, especially when the military’s involvement is colored by politics. President Andrew Jackson’s 1834 deployment of federal military force to quash labor unrest along the Chesapeake and Ohio (C&O) Canal, for instance, called into question whether the military was used as a tool to shore up the fortunes of the canal company’s president, John Eaton, who served as Jackson’s former secretary of war and was also a close friend of the president.
Domestic deployments to the former Confederate states during Reconstruction following the Civil War prompted widespread backlash from white Southerners amid accusations of military intrusion in civilian life. Though federal troops largely worked to protect the rights and safety of newly freed Black citizens, this backlash ultimately precipitated the enactment of the Posse Comitatus Act in 1878, which generally prohibited the use of federal troops for civilian law enforcement unless expressly authorized by the Constitution or Congress. Though the Act had its roots in white Southern lawmakers’ desire to end Reconstruction, it codified the boundaries that have since separated the duties of the U.S. armed forces from those of civilian law enforcement — a foundation of U.S. civil-military relations.
Over the next century, episodes of civil strife, labor protests, campus unrest, and the struggle for civil rights continued to shape debates on how, whether, and why to deploy federal military force domestically. Some interventions, like the Army’s heavy-handed ambush of World War I veterans during the Bonus Army March in 1932, clearly illustrate how hasty and politically charged deployments degrade the chain of command and harm the military’s reputation. Others, including the use of the military to enforce constitutional rights in the South during the Civil Rights era, alternatively demonstrate how the judicious deployment of military personnel can help uphold the rule of law under the most extraordinary of circumstances.
Across generations, the distinct roles of the U.S. military and domestic law enforcement have been acknowledged and respected — and, in most cases, consensus emerged as to the need to reinforce this cornerstone of civil-military relations when missions strayed from this north star. The pattern has been consistent over time: escalations of unrest, disillusionment in the ranks, and politicization of the armed forces are the regrettable outcomes of most military interventions in civilian law enforcement.
These dynamics conspire to undermine military readiness and, as a result, national security. “By diverting focus and resources away from core national security competencies, domestic military operations frequently result in a degraded security environment,” we write in the report. “Given their vulnerability to autocratic abuse, domestic military interventions in civilian law enforcement necessitate a high degree of skepticism — especially when troop deployments are driven by political considerations rather than as a genuine measure of last resort.”
Contemporary Examples from Abroad
Skepticism of military policing was deeply ingrained in the Founding Fathers’ generation, born of experience under the heel of British military occupation. This instinct has since informed policymakers and leaders around the world, as other democracies sought to establish similar boundaries between national security and the responsibilities of civilian law enforcement. Aspiring autocrats worldwide have, unsurprisingly, repeatedly tried to collapse this distinction to consolidate power and suppress opposition.
Even in established democracies, though, political leaders have succumbed to the temptation of deploying military personnel in response to domestic security crises. Although military intervention might be warranted in extraordinary cases when unrest truly overwhelms civilian authorities, escalation, disillusionment, and politicization are the most likely outcomes of domestic deployments that exceed measures of last resort. Once a military is pulled into domestic affairs, its readiness to manage foreign threats is degraded while simultaneously elevating the potential for violence and lawlessness at home.
While these trends can be observed all over the world, a few illustrative examples make the point.
Mexico
Recent Mexican history demonstrates the clear escalatory risks that accompany using the armed forces for civilian law enforcement. In 2006, President Felipe Calderón launched a “war on drugs” to address cartel violence that eventually sent military units across most of Mexico’s states. By the end of his term in 2012, the cartels were by all measures more robust and the public was no safer. But the pattern of escalation continued as Calderón’s successors moved forward with increased domestic troop deployments, peaking under former President Andrés Manuel López Obrador.
Following the military’s domestic interventions, homicides increased along with human rights abuses committed by federal security forces. As we explain in the report,
These spikes in violence were most pronounced in areas with the highest troop concentrations, where domestic military operations more often resulted in excessive force against civilians — reflecting the fundamental mismatch between the military’s combat training and the de-escalation skills required for civilian policing. Arbitrary arrests, disappearances, and extrajudicial killings rose alongside the military’s expanded policing role.
The reputation of the Mexican armed forces for neutrality and professionalism cratered after its foray into domestic law enforcement, and the country continues to endure significant security challenges from entrenched criminal organizations.
France
In the aftermath of the January 2015 Charlie Hebdo attack, France launched Operation Sentinelle which, following a subsequent terror attack in Paris later that year, deployed 10,000 soldiers domestically with the aim of providing a visual deterrence. Military patrols around tourist sites became commonplace –– drawing critics from inside and beyond the military who deemed the operation ineffective and, counterproductively, exposed troops to heightened risk. Though the serious threat of domestic terror at the time warranted a strong response from the state security apparatus, the operation stoked disillusionment and morale problems in the ranks, exacerbated by the mismatch between the military’s combat mission and the responsibilities of internal security.
Seven years into the still-ongoing operation,
a government audit concluded that the operation prioritized optics over military utility, echoing concerns that what began as a temporary mission has become a seemingly indefinite fixture of France’s security architecture — compromising operational readiness, force retention, and the military’s external defense responsibilities.
Brazil
For decades, Brazilian presidents have used troops to combat violent crime in Rio de Janeiro – fostering additional violence in some instances while achieving few long-term security gains. Ordering troops into the nation’s biggest city to appear “tough on crime” is a distinctly political mission, one that by its nature is bound to divide the citizenry against its own armed forces.
President Jair Bolsonaro oversaw the most sweeping expansion of the military’s domestic role since the end of Brazil’s military dictatorship, repeatedly raising the spectre of using the armed forces to resolve political disputes, including with Brazil’s Supreme Court. Bolsonaro’s renewed militarization and side-stepping of norms foreshadowed the near-total breakdown of the civil-military divide at the end of his presidency, when a doomed coup plot to overturn his 2022 presidential election defeat culminated in the January 2023 storming of Brazil’s Congress, Supreme Court, and presidential palace by a mob of his supporters.
“Although the plot failed due to a lack of institutional support from the heads of the army and air force, it exposed the corrosive effects of the military’s years-long intervention in civilian affairs,” we write in the report. “By the time Bolsonaro left office, the military’s expanded internal role politicized the armed forces, while also contributing to steep democratic backsliding and persistent threats to the rule of law.”
The Trump Administration
The abrupt deployment of federalized National Guard and Marines to Los Angeles. Attempted federalization of National Guard in Portland and Chicago. Hybrid deployments in Memphis and New Orleans. Threats to deploy troops to other cities governed by the president’s political opponents. Massive expansion of National Defense Areas to facilitate military assistance with immigration enforcement along the border. The Trump administration’s efforts to deploy the military domestically over the objection of local and state leaders, and for questionable law enforcement purposes, threaten to erode the critical line between the military and domestic policing.
Thousands of National Guard troops remain deployed in Washington, D.C., where the unique status of the District complicates the rules governing use of the Guard. Plus, the administration has announced plans to deploy thousands more Guardsmen from around the country to D.C. this summer. Yet, independent research confirms the same dynamic commonly observed in other domestic policing missions: the effort has had “no measurable effect on violent crime.” Not only are domestic deployments expensive, but they carry heavy costs for our national interest: an escalated threat of violence and bodily harm to civilians and troops alike, disillusionment in the ranks, and the politicization of the armed forces and accompanying degradation of its capacity to fulfill its primary mission – protecting the national security of the United States.
To their credit, federal courts have taken these issues seriously, affirming a clear and substantial role for judicial review of domestic deployments. In December, the Supreme Court foreclosed the administration from using the novel legal theory it advanced to justify the orders to deploy in Los Angeles, Portland, and Chicago. Indeed, timely judicial orders ensured that no troops were actually deployed in Portland and Chicago. The Supreme Court’s ruling went out of its way to emphasize the Posse Comitatus Act’s general prohibition on military policing. And in Los Angeles, a federal judge ruled that many of the actions taken by deployed troops were, in fact, violations of that long-standing protection.
A federal judge in D.C. likewise concluded that the D.C. deployment was unlawful, and the government’s appeal of that ruling remains pending before the D.C. Circuit. It’s unclear whether courts elsewhere around the country will be scrutinizing domestic military activity in the coming months, with the administration promising a standing National Guard force ready for “rapid nationwide deployment,” and Secretary of Defense Pete Hegseth refusing to disavow the possibility of troop deployments during the fall elections. What we do know is that those of us concerned with protecting public safety and upholding national security should remain skeptical of any effort to normalize and expand the military’s domestic footprint, which is doomed to degrade security and threaten the longstanding boundaries governing healthy civil-military relations.
