Military Deployment In Law Enforcement: Legal Or Not?

The use of active-duty military personnel for law enforcement is a highly debated topic. While the Posse Comitatus Act of 1878 prohibits the use of the military for civilian law enforcement, there are exceptions to this rule, such as in the case of national emergencies or with explicit authorization from Congress. The Insurrection Act of 1807 further restricts the president's ability to deploy active-duty troops on American soil, except under specific circumstances. However, in recent years, there have been calls for the military to 'participate actively' in law enforcement, particularly in times of civil unrest or for immigration enforcement. The use of the military in such roles has raised concerns about the potential violation of constitutional rights and the impact on military readiness.

The Posse Comitatus Act of 1878

The Posse Comitatus Act was passed as an amendment to an army appropriation bill following the end of Reconstruction and has been updated several times since its enactment. The original Act only applied to the US Army, but amendments over the years have expanded its scope to include the Air Force, Navy, Marine Corps, Space Force, and Coast Guard. The Coast Guard, while part of the armed forces, has explicit statutory authority to perform law enforcement duties and is not bound by the Posse Comitatus Act.

The Posse Comitatus Act states that anyone who "willfully uses any part of the Army or the Air Force as a posse comitatus or otherwise to execute the laws shall be fined, imprisoned, or both." This means that military personnel subject to the law may not participate in civilian law enforcement unless expressly authorized by a statute or the Constitution. The Act does not apply to the National Guard or Reserve units under state jurisdiction, which can be used by state governors to assist with law enforcement during emergencies, civil unrest, or disasters.

There are exceptions to the Posse Comitatus Act, such as the Insurrection Act, which allows the President to deploy the military to suppress an insurrection or enforce federal law in a state. In addition, the President may use the military to protect a group of people's civil rights when the state government is unable or unwilling to do so. However, these exceptions are not considered constitutional exceptions, as the Act only allows for express exceptions authorized by Congress or the Constitution.

The Insurrection Act of 1807

In 1861, a new section was added to the Insurrection Act, allowing the federal government to use the National Guard and armed forces against the will of the state government in the case of "rebellion against the authority of the government of the United States." This amendment was made in anticipation of continued unrest after the Civil War. The Insurrection Act was the legal basis for Abraham Lincoln to send federal troops into Southern states during the Civil War.

In 1871, the Third Enforcement Act revised the Act to protect Black Americans from attacks by the Ku Klux Klan. This amendment allowed the federal government to enforce the Equal Protection Clause of the Fourteenth Amendment to the United States Constitution. This section was invoked during the Reconstruction Era and the Civil Rights Era during desegregation fights.

The Insurrection Act has been used multiple times in history, including by Eisenhower and Kennedy to enforce desegregation, and by Johnson to quell uprisings in Chicago, Baltimore, and Washington, D.C., in 1968. More recently, George H. W. Bush invoked the Act to send troops to Los Angeles during the 1992 Rodney King protests.

The Insurrection Act, along with the Posse Comitatus Act, restricts how active-duty military forces can be deployed on American soil. The Posse Comitatus Act of 1878 prohibits the use of U.S. military forces for civilian law enforcement purposes unless explicitly authorised by Congress. The Insurrection Act provides a "statutory exception" to the Posse Comitatus Act, allowing the president to deploy the military to assist civilian authorities with law enforcement. However, the Insurrection Act has been criticised for being too vague and granting significant power to the president to decide when and where to deploy the military domestically.

Use of military force as a last resort

The use of military force as a last resort is a long-standing principle of international law and a fundamental norm of international relations. It is enshrined in the United Nations Charter, which states that "all Members shall settle their international disputes by peaceful means in such a manner that international peace and security, and justice, are not endangered." This principle has been interpreted to mean that the use of military force should be a last resort, only used when all other peaceful means of resolving a dispute have been exhausted.

In the United States, the use of military force as a last resort is also a legal requirement, although it has not always been followed in practice. The Posse Comitatus Act of 1878 prohibits the use of the US military to perform the tasks of civilian law enforcement unless explicitly authorized by Congress. Similarly, the Insurrection Act of 1807 restricts the President's ability to deploy active-duty military forces on American soil, except in cases of domestic violence, insurrection, natural disaster, or epidemic.

Despite these legal restrictions, there have been several instances in which the US military has been deployed domestically, such as during the terror attacks of 9/11, Hurricane Katrina, and along the US border with Mexico. These deployments highlight the complex and sometimes ambiguous nature of the laws governing the use of military force, particularly when it comes to domestic deployment.

To ensure that the use of military force truly is a last resort, several measures can be implemented. Firstly, existing Authorizations for the Use of Military Force should be repealed, and any future authorizations should have firm limitations, including an expiration date, geographic constraints, a well-defined mission, and a clear definition of what constitutes a "combatant". Secondly, military involvement in ongoing conflicts, such as Afghanistan and Iraq, should be ended, and the US should pursue good-faith engagement through diplomatic, economic, and humanitarian means instead. Finally, to fully understand the costs of armed conflict and reduce civilian casualties, full casualty reporting should be reinstated, and humanitarian efforts should be fully funded in regions affected by US military engagement.

National Guard troops for law enforcement

The Posse Comitatus Act of 1878 prohibits the use of US military forces for civilian law enforcement tasks such as arrest, apprehension, interrogation, and detention, unless authorized by Congress. However, National Guard units are not subject to the Posse Comitatus Act because they are under state jurisdiction. This means that state governors can deploy National Guard troops to assist with law enforcement during emergencies, civil strife, disasters, or civil unrest.

The Posse Comitatus Act does not apply to members of the National Guard in a state status authorized by US Code Title 32 and under the command and control of their respective state or territorial governor. In such cases, National Guard troops can be used for law enforcement if doing so is consistent with state law.

The District of Columbia (DC) National Guard is an exception, as it is always under presidential control. The DC National Guard normally operates in a Title 32 status, which means that while Guard personnel are paid with federal funds, they remain under state command and control. This allows the president to use the DC National Guard for law enforcement purposes.

While National Guard troops can be used for law enforcement purposes, there are considerations regarding the costs and effectiveness of deploying them for such missions. Using the National Guard may simply be a way to diffuse costs across different budgets, and a quick reaction force of civilian police officers may be a wiser option in some cases.

Active-duty military for immigration enforcement

The use of active-duty military forces for law enforcement purposes on domestic soil is restricted by two federal laws: the Insurrection Act of 1807 and the Posse Comitatus Act of 1878. The Posse Comitatus Act prohibits the use of active-duty troops for civilian law enforcement, except when expressly authorized by Congress.

Despite these restrictions, there has been a growing trend since the 1980s of military participation in immigration enforcement at the US-Mexico border. This includes the deployment of active-duty soldiers by the Biden administration in 2024, as well as the federalization of the National Guard forces at the border. While National Guard forces are not subject to the Posse Comitatus Act, they have provided support to DHS in non-core law enforcement activities, such as surveillance, transportation, and the provision of equipment.

The increasing militarization of the southern border has generated alarm, as it stigmatizes migrants and asylum seekers and undermines core democratic values and legal principles. The National Guard forces operating in Title 32 status are subject to state law, which may limit their ability to engage in arrests or similar law enforcement activities. However, under the Insurrection Act, the President can deploy active-duty armed forces and federalize the National Guard, potentially expanding their role in immigration enforcement.

While the Department of Defense can provide military equipment, training, and support for counterdrug or counter-transnational crime activities, the use of federal military forces for immigration enforcement violates the American tradition of rejecting military interference in civilian affairs. This interference is seen as a threat to democracy and individual liberty, which the Posse Comitatus Act aims to protect.

Frequently asked questions