Deploying Soldiers on American Soil: Operational Risks & Considerations

Different training rules, operational risks, and past experience caution restraint.

Beyond the concerns outlined in earlier writings by Jack Goldsmith, Laura Dickinson, Bob Bauer, the Brennan Center, and myself, numerous operational considerations guide any decision to deploy troops on U.S. soil. There are three operational factors that must inform any decision to deploy troops on American soil. Taken together, these three factors caution restraint. They include:

• The role of military regulations in defining domestic deployments. 
• How military norms limit domestic deployments.
• Why the military is rightly concerned about deployments that don’t align with military capabilities and training.

The Role of Military Regulations in Limiting Domestic Deployments

The Department of Defense interprets its authority to deploy the military domestically via two key instructions: DoD Instruction 3025.18, “Defense Support of Civil Authorities (DSCA); and DoD Instruction 3025.21, “Defense Support to Civilian Law Enforcement Agencies.”

Under Pentagon regulations, federal military forces are defined as “Army, Navy, Marine Corps, and Air Force personnel (including Reserve component personnel) on Federal active duty and National Guard personnel when under Federal command and control.” Within these forces, each military service has its own unique culture, skills, doctrines, and training, all of which impact and influence any potential domestic deployment.

The first instruction (DSCA) addresses how the military deploys in support of the DSCA mission at home. Defense Support to Civil Authorities is a mission that is triggered when a civil authority requests military assistance—this might include disaster response, a special event, or other domestic emergency. In fact, thousands of National Guard personnel are being deployed under this authority to support Hurricane Helene disaster response efforts. The Pentagon uses six criteria in evaluating any request from civil authority: 

1. Legality (compliance with laws).
2. Lethality (potential use of lethal force by or against Defense Department forces).
3. Risk (safety of Defense Department forces).
4. Cost (includes source of funding and effect on the Defense Department budget).
5. Appropriateness (whether providing the requested support is in the interest of the department).
6. Readiness (impact on the Defense Department’s ability to perform its other primary missions).

In addition, Pentagon regulations prohibit the military from participating in certain activities, regardless of the urgency of the request. For example, both federal military forces and National Guard forces (regardless of status) are prohibited from “conduct[ing] operations at polling places.” This regulatory prohibition is rooted in a criminal statute that prohibits any officer ordering any “troops or armed men” to a “place where a general or special election is held.” For the upcoming November election, the military should not be anywhere near a polling location. 

The second instruction, “Defense Support to Civilian Law Enforcement,” addresses exceptions to the 1878 Posse Comitatus Act. The Posse Comitatus Act prohibits federal military forces from being deployed “to execute the laws” absent a statutory or constitutional exception. In addition to the Insurrection Act, the Pentagon delineates around 20 distinct statutory exceptions to the Posse Comitatus Act.

This regulation highlights that military leadership will scrutinize any order to provide direct assistance to law enforcement. And military leaders need—indeed, require—clear orders from their civilian leaders before they take on any mission. What’s more, Pentagon regulations highlight that federal military forces deployed in support of law enforcement operations shall maintain the primacy of civilian authority at all times. Further, Pentagon regulations state that federal military forces to control civil disturbances shall occur only in a specified civil jurisdiction under specific circumstances. So, a nationwide activation of military forces for an unspecified time and location would be inconsistent with existing regulations, past practice, and the military’s general skepticism of playing an outsized role in law enforcement operations.

Even when a federal military force is deployed under the Insurrection Act (or other exception to the Posse Comitatus Act), the military is deployed in a support role to the relevant civilian law enforcement agency. Placing the military in a support role acknowledges the importance of maintaining civilian control of the military—a long-standing norm since the nation’s founding. Further, maintaining civilian control of any law enforcement operation with outside military members is similarly important from a mission perspective. After all, civilian law enforcement agencies are more familiar with local circumstances, have a deeper understanding of applicable state and local laws, and possess more extensive police training.

How Military Norms Limit Domestic Deployments

While the Insurrection Act authorizes federal military forces to be deployed domestically in a law enforcement capacity, state and local governments have the primary authority and responsibility to protect life and property as well as to maintain order in civilian communities. Culturally, the military has a strong allergic reaction to engaging in crime-fighting more broadly—even when requested to do so. 

The historical reluctance to deploy the military domestically can be traced back to the nation’s founding and long-standing concerns of a standing army meddling in domestic affairs. After all, America was born of revolution, with the original colonies declaring their independence in part due to the quartering of British military troops in colonists’ homes. This pre-constitutional military intrusion into civilian affairs led Thomas Jefferson to write in the Declaration of Independence that King George “kept among us, in times of peace, Standing Armies, without the Consent of our legislatures [and] Quarter[ed] large bodies of armed troops among us … [while] affect[ing] to render the Military independent of and superior to the Civil power.” And the U.S. Constitution enshrines long-standing concerns of a standing army by prohibiting Congress from appropriating money “to raise and support Armies … for a longer Term than two Years.” This clause ensures that Congress addresses the issue of a standing army every two years through its funding power, with the intention of placing a fiscal check that would prevent the president from amassing a large standing force.

The United States has a rich tradition of civilian control of the military that has limited the military’s role in day-to-day domestic involvement in civilian affairs. This restraint reflects a special trust and bond that acknowledges civilian control of the military while excluding the military from domestic political matters—witness the express prohibition of military operations around polling locations. 

A few recent examples add context to the norm limiting the military’s role in day-to-day civilian matters. 

The military’s reluctance to respond to requests to maintain law and order was perhaps best personified by the pushback from the military commander during the height of the Los Angeles riots. In fact, once President George H.W. Bush invoked the Insurrection Act to federalize the California National Guard, the military commander approvedonly 20 percent of requests for law enforcement support. Prior to the Insurrection Act’s invocation, the state-led California National Guard was approving “virtually 100 percent” of law enforcement requests. The police, media, and public expected federal military forces to keep the peace, but the military commander expressed a strong reluctance to actively engage in law enforcement functions. Maj. Gen. Marvin Covault, the military commander of federal forces, stated, “It was not the military’s mission to solve Los Angeles’s crime problem, nor were we trained to do so.” Gen. Covault was not alone in this sentiment—senior military leaders consistently pushed back during efforts to expand the military’s role in counterdrug operations throughout the 1980s and 1990s. 

Indeed, Congress sought to increase the military’s role in counterdrug operations in the 1980s, but Congress faced significant pushback from senior Pentagon leadership who were reluctant to take on missions outside of traditional military functions. Testifying before Congress in 1988, Secretary of Defense Frank Carlucci pushed back against congressional efforts to require the military to engage in counterdrug operations. Carlucci stated that imposing a broader counterdrug mission on the Pentagon stressed military resources. He also expressed concerns about the military’s institutional competence to handle a law enforcement mission set. Testifying before Congress, Secretary Carlucci stated, “The Armed Forces should not become a police force, nor can we afford to degrade

readiness by diverting badly needed resources from their assigned missions.”

In the same hearing, the chief of naval operations, Adm. Frank Kelso, highlighted the Navy’s lack of institutional training to conduct law enforcement missions while noting that the Navy would face a readiness concern if a sailor was asked to testify in federal court while deployed overseas. And coordination between military forces and civilian law enforcement agencies poses challenges due to differences in command structures, communication protocols, terminology, and operational priorities.

Consider what happened during the 2020 protests and the tense relationship between senior military leaders and the president over the use of military force at home. Then-President Donald Trump’s legal team drew up an order to invoke the Insurrection Act to use federal military forces to quash protests. President Trump never invoked the Insurrection Act but instead turned to a previously obscure provision that allows outside National Guard members to deploy to perform “training or other duty.” 

The chairman of the Joint Chiefs of Staff, Gen. Mark Milley, was joined by Secretary of Defense Mark Esper in not supporting the draft Insurrection Act order. Esper explicitly rejected the idea of invoking the Insurrection Act at a news conference. And Milley issued a memo to the entire joint force, reaffirming that service members “swear an oath to support and defend the Constitution and the values embedded within it.” Milley highlighted the importance of upholding the ideals embodied in the Constitution as well as “upholding the values of our nation.” And Milley publicly apologized for appearing in uniform with President Trump during a photo op in Lafayette Square, stating, “My presence in that moment and in that environment created a perception of the military involved in domestic politics … and we must hold dear the principles of an apolitical military that is so deeply rooted in the very essence of our republic.”

Milley’s memo and extraordinary public apology reflected a sober recognition that the military holds a special role in civil society. And intrusion into civil society—even if legally authorized—should only be ordered in extraordinary circumstances. There exists a special trust between military service members and the American people that the military swears to protect. 

While Gen. Milley has since retired, any mass invocation of the Insurrection Act will likely face a similar reaction from the new senior uniformed leader, Gen. Charles Q. Brown. During his confirmation hearing for chairman of the Joint Chiefs of Staff, Brown reaffirmed that the military must stay nonpartisan and nonpolitical and must “stay out of politics.” In recent days, Reps. Mikie Sherrill (D-N.J.) and Elissa Slotkin (D-Mich.) have asked both Secretary of Defense Lloyd Austin and Gen. Brown to agree that an actual insurrection or rebellion must exist for the military to deploy pursuant to the Insurrection Act.

Why the Military Is Rightly Concerned About Deployments That Don’t Align With Military Capabilities and Training

Beyond these legal authorities and governing regulations, federal military forces often lack the requisite training and expertise to conduct law enforcement (the military calls this “civil disturbance operations”). To be sure, there are select law enforcement units that have specialized law enforcement training, but most federal military forces do not. This lack of training requires a sharp shift in mindset from warfighter to law enforcer when a service member is asked to conduct civil disturbance operations. This shift increases the likelihood of a mistake in an already challenging and chaotic operational environment. The Department of Justice has long recognized the challenges of deploying U.S. troops domestically for law enforcement functions, noting in 1964 that federal military forces have little law enforcement training.

Shifting Rules When to Use Force

Transitioning from warfighter to law enforcer requires an entirely new set of instructions governing when to use force. More permissive Standing Rules of Engagement (SROE) no longer apply domestically, and military forces must adopt and apply the more restrictive Standing Rules for the Use of Force (SRUF). SRUF takes into account cornerstone constitutional protections. Indeed, applying SRUF inappropriately could well undermine constitutional rights, such as the Fourth Amendment’s protection against unreasonable searches and seizures and the First Amendment’s protection of free speech and assembly.

As a general matter, military forces are trained for combat and an operational environment that rely on the much more permissive SROE. In contrast, the law enforcement-oriented SRUF apply when federal military forces conduct law enforcement operations. 

I previously explained this dangerous disconnect between SROE and SRUF here:

As a general matter, ROE govern military operations in environments where host-nation law enforcement and civil authorities are nonexistent or otherwise resistant to the U.S. military presence. Rules of engagement involve a more “combat-mindset.” It may even involve a declaration that certain forces are hostile, whether or not the individuals pose an imminent threat of death or serious personal injury. Rules of engagement are employed largely outside the U.S. in uncertain environments …. In contrast, rules for the use of force (“RUF”) are based on a law enforcement and self-defense mission and mindset to include this border deployment. It takes into account domestic legal considerations: This includes the Posse Comitatus Act, the 4th Amendment and existing constitutional provisions. Rules for the use of force cannot authorize force in excess of constitutional reasonableness, nor can it declare certain forces hostile.

 Beyond the necessary shift from permissive, operational SROE to the more restrictive law enforcement SRUF, the federal military force will likely be operating alongside state National Guard units that have yet to be brought under federal command and control. In that circumstance, state National Guard units would follow yet another set of rules governing when to use force—rules established by state law. These National Guard forces normally comply with state-specific rules addressing enforcement authority and use of force. In some states (such as Arkansas), National Guard personnel have broad arrest authorities, while in other states (such as Iowa or New York), the National Guard normally has only those powers enjoyed by the population at large. Each state and territory has different guidance on National Guard authorities on the use of force and when it is authorized. Different rules create another potential for confusion when federal military forces operate alongside state National Guard forces. 

Once again, the military response to the 1992 Los Angeles riots provides a cautionary tale. President George H.W. Bush received a request from California Gov. Pete Wilson in 1992 to tamp down violence in the aftermath of the Rodney King acquittal. This request came after the California National Guard and local police were unable to suppress acts of violence. Bush honored this request, invoking the Insurrection Act by initially deploying soldiers from the 7th Infantry Division at nearby Fort Ord and Marines stationed at Camp Pendleton.

The California National Guard served in a state command under Gov. Wilson. Under state active-duty status, the California National Guard initially followed state rules for the use of force as they were not initially federalized. The California National Guard worked alongside federal military troops who followed altogether rules for the use of force (not rules of engagement). Twelve hours later, President Bush federalized the California National Guard, who now had to comply with SRUF—entirely different rules. 

Confusion reigned. A domestic “fog of war” took hold—the California National Guarddid not even realize that it had been federalized for a full 24 hours. A week later, the California National Guard reverted to state status (another change in rules) while federal military forces remained in the area and gradually redeployed back to their respective bases. 

Experience as Cautionary Tale

Mistakes from the past should guide any decision to deploy the military on American soil. Consider the following two examples.

First, in the 1990s, President Bill Clinton ordered Marines to the U.S.-Mexico border to assist with counterdrug operations in an effort to stem the tide of the cross-border drug trade. In a tragic case, a young Marine killed Esequiel Hernandez, an American high school student in Redford, Texas, who was shepherding goats along the border. While the exact circumstances of the shooting have been disputed for years, members of Congress highlighted the inherent dangers of arming Marines at the border. This tragic death led to the temporary halting of the military presence at the border. What’s more, the tragic killing conducted at the hands of heavily camouflaged Marines showcased the disconnect between core military training and doctrine that emphasize combat in hostile environments in contrast to civilian law enforcement training that emphasizes protection of the local community while upholding constitutional protections. 

Second, in the 1992 Los Angeles riots, U.S. Marines, trained as warfighters in the more combat-oriented rules of engagement accompanied a police officer to a domestic dispute in a neighborhood. The police officer instructed the Marines to “cover me” as he approached the door. For law enforcement, “cover me” meant to point your weapons and be prepared to respond if necessary. The Marines interpreted “cover me” in accordance with their training and immediatelylaid down a base of heavy fire, ultimately firing over 200 bullets into the house. Thankfully, no one was hurt in the particular incident, but this vignette showcases how different training and terminology can risk lives, lead to confusion, and add to the fog of military operations.

In sum, federal military forces must comply with the more restrictive rules for the use of force, which must be boiled down to tactics, techniques, and procedures that operationalize these rules to different scenarios. And this may be the first time that military forces operate in the SRUF construct. This training disconnect may lead to excessive use of force or inappropriate responses in a domestic law enforcement environment.

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In sum, deploying military forces domestically can divert resources and attention from their primary national defense missions, potentially impacting military readiness.The use of military forces in domestic law enforcement can be seen as a political act, leading to accusations of partisanship and potential misuse of power for political gain. Beyond the considerations outlined above, the National Guard is a stressed force after the coronavirus pandemic, which witnessed the largest domestic military deployment in recent history.

Any decision to use the military as a law enforcer must take into account existing regulations, existing norms, training, and operational considerations discussed above. While the Insurrection Act is a powerful authority, the primacy of the civilian authority throughout civil disturbance operations reinforces that any support to law enforcement provided by the military is just that—support. 

– Mark Nevitt, Published courtesy of Lawfare.