Everything You Need to Know About Martial Law

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National Guardsman patrol Chicago during martial law in 1968
National Guardsmen patrol the streets in Chicago following rioting and arson that ensued after the news of the assassination of Dr. Martin Luther King, Jr., April 6, 1968. (AP Photo)

What is martial law? While there is no universal definition, the term often refers to the use of the military for law enforcement. But contrary to popular belief, simply calling up federal or state military members to assist during times of natural emergency or civil unrest is not necessarily the same thing as implementing martial law.

Looking at the history of laws surrounding the use of the military in law enforcement can also give some clues as to what American scholars and officials consider martial law today.

What Is Martial Law?

While not specifically defined in the U.S. Constitution, many legal experts consider martial law to be the use of military personnel to dramatically assist or completely replace a nation's normal legal system in times of emergency. Whether any given use of the military rises to the level of martial law is tied to exactly how much military support or action is used.

Under total martial law, the normal American law enforcement and legal system is replaced by a stricter set of laws and punishments that is completely controlled by the military or executive branch of the government. The normal checks and balances system built into the Constitution is suspended.

Though debated in some legal discussions, martial law can also occur in stages, without ever getting to total takeover by the military. Under current U.S. law, the president, Congress or a local military commander may impose degrees of martial law under specific situations.

Related: 6 Times Martial Law Was Declared and the Constitution Suspended in the United States

Who Can Declare Martial Law?

Martial law can be declared by the U.S. president, the governor of a state or, in limited emergencies, by a local military commander. How and when it is declared is governed by a series of laws.

Examples of Martial Law in the U.S.

The first time martial law was declared in the U.S. was in New Orleans by General Andrew Jackson during the War of 1812, though the decision was unpopular with both the public and the other branches of government. Jackson was fined $1,000 by a judge for having a reporter who wrote an article critical of the measure arrested, though he later used his influence after leaving the presidency to convince Congress to pass a special law to get him his money back.

All told, martial law has been declared in the U.S. about 68 times, according to the Brennan Center for Justice, a nonpartisan law and policy institute. Most of those 68 cases of federal troops being deployed within the U.S. borders involved labor unrest (29 times), and those 68 invocations of martial law have resulted in about 33 separate legal challenges to the declaration. Martial law was last officially declared in the U.S. in 1963.


Related: 6 Times the Military was Used for Riot Control in the US

Martial law has twice been implemented nationally by a president during wartime, first by Abraham Lincoln in border states between the North and South during the Civil War, and then again by local military officials in Hawaii during World War II. This was later approved and expanded by Franklin Roosevelt's executive order to include the incarceration of Japanese-Americans on the West Coast. Both martial law declarations were challenged in court, and both times, the courts ended up ruling that at least a portion of those implementations were unconstitutional or too broadly applied.

In fact, nearly every time active-duty troops have been mobilized for law enforcement within the U.S., there has been backlash throughout the nation, with debates for and against it lasting years.

In several examples of martial law -- such as when President George W. Bush placed foreign detainees in a prison in Guantanamo Bay, Cuba, outside of U.S. court jurisdiction and was later overruled by the Supreme Court, or a loophole in current law that gave President Donald Trump control of all D.C. National Guard troops deployed to the district during the Jan. 6, 2021, insurrection at the Capitol -- Congress and the courts have usually reacted swiftly and strongly to any domestic military deployments. Since martial law sidesteps the constitutional division of powers and grants additional, emergency powers to the executive branch, such events do not usually sit well with the other branches of government.

Two laws enacted as the result of previous actions include the Insurrection Act and the Posse Comitatus Act. Both are now widely used in emergency situations, even though their constitutionality is still often called into question more than 100 years after they were enacted. The Insurrection Act spells out the only times that federal forces may be used in a domestic role while the Posse Comitatus Act limits their use in those circumstances.

Examples of Non-Martial Law Troop Use in the U.S.

Federal troops can be used to enforce law and order without an official declaration of martial law. In the U.S., they have been utilized at least 14 times under the Insurrection Act before the 1990s and 23 times since 1992 under the Posse Comitatus Act, according to the Congressional Research Service.

In 1932, President Herbert Hoover famously directed the military to clear protesting veterans and their families from an encampment near the U.S. Capitol, where they were protesting delays in payments of their war bonus. Douglas MacArthur and George Patton were both involved in the operation, which involved tanks and soldiers with fixed bayonets clearing a camp full of veterans and their families. It did not sit well in the court of public opinion.

Here are some other examples of recent federal troop domestic deployments by decade:

  • 1950s -- President Dwight D. Eisenhower used federal troops to enforce school integration in Arkansas;
  • 1960s -- President Lyndon Johnson used them to quell riots after Martin Luther King Jr.'s assassination;
  • 1970s -- President Richard Nixon used them to stop anti-war protests, including those at Kent State University in Ohio;
  • 1980s -- President George H.W. Bush used troops to end looting after Hurricane Hugo;
  • 1990s -- President Bill Clinton used them to aid a siege of a religious sect headquarters in Waco, Texas;
  • 2000s -- President George W. Bush used troops to prevent looting following Hurricane Katrina;
  • 2010s -- President Barack Obama used them during the occupation of a National Wildlife Refuge by political extremists;
  • 2020 -- President Donald Trump used them during racial unrest.

What Is the Insurrection Act?

The Insurrection Act of 1807 gave the president the ability to deploy active duty and National Guard troops within the U.S. when necessary. Troop activation is authorized:

  • When requested by a state's legislature. If the legislature can't be rapidly convened, the governor can also request federal assistance during an insurrection within that state.
  • If an insurrection occurs in a state, and that state cannot or will not provide for the protection of its citizens, federal forces may be deployed to maintain order.
  • If there is an insurrection in any state making it impracticable to enforce the law in any other state, those states may request federal assistance.
  • If a state fails to provide federally guaranteed rights, federal assistance may be allowed to protect the citizens.

The president must first issue a proclamation ordering insurgents to disperse before he may invoke the Insurrection Act.

What Is the Posse Comitatus Act?

The Posse Comitatus Act, first enacted in 1878, basically prohibits federal forces from assisting in domestic law enforcement unless the president has directed operations under the Insurrection Act or related laws. It is the legal precedent in use during most military involvements in civilian activities today.

It was originally enacted as both a reaction to Lincoln's invocation of martial law during the Civil War to use military courts to try civilians, and to protect freed slaves from mistreatment in the newly liberated post-secession states.

The act allows military personnel to only assist civilian police in enforcing existing laws, while granting authority for the federal government to ensure federal rights are unilaterally provided and enforced nationwide.

Related: Everything You Need to Know About the Military Draft

Mobilizing the National Guard for Martial Law

Most state constitutions allow for the state's government to mobilize their National Guard troops in a law enforcement activity within their state. States often also have agreements with each other that allow troop deployments to neighboring states during emergencies. When serving in either a state or Title 32 status, typically reserved for activations around natural disasters, Guard members may enforce their state's laws.

However, if Guard members are called into federal service, they become part of the federal armed forces and, as a result, are limited in their duties by the Posse Comitatus Act.

What Can the Military Do During Martial Law?

Normally, active-duty troops may only perform domestic duties related to national defense. That includes such things like counterterrorism, drug interdiction or dealing with weapons of mass destruction. If a situation exists that requires the military to serve in a law enforcement role, it must be authorized in writing by the president or, in an emergency, by the local military commander.

Federal troops acting under the Posse Comitatus Act are limited to only performing the duties of a deputized posse to assist civilian police in enforcing existing laws. In fact, the military is severely limited in exactly what duties it may perform when assisting civilian police, rules spelled out in DoD Instruction 3025.21. Army Doctrine ADP 3-28 also details defense support of civilian authorities.

Federal military forces assisting in civilian law enforcement must remain under federal military command and control at all times.

Local military commanders also have the authority to temporarily deploy federal troops to keep the order during large-scale unexpected civil disturbances that threaten order or may cause significant loss of life or destruction of property.

Limitations on Martial Law

Law enforcement support during martial law falls into two broad categories: direct and indirect. Direct support involves enforcing the law and engaging in physical contact with offenders. Indirect support consists of aid to civilian law enforcement agencies, but not enforcement of the law or direct contact with offenders.

  • Indirect support includes logistics, transportation and training assistance, except in life-threatening emergencies.
  • Direct support includes performing search operations or criminal investigations, making arrests, pursuit and even traffic control.

Military members in a Title 10 federal activation status may not be involved in direct civilian law enforcement activities unless expressly authorized by the president, U.S. constitution or act of Congress. There are very specific rules for use of force by military personnel.

Laws even exist preventing DoD from using unmanned aircraft systems (drones) to assist civil authorities without specific approval from the secretary of defense and preventing troops from conducting any operations at a polling place unless it is necessary to "repel armed enemies of the United States."

Martial Law in the U.S. Today

While the executive branch of the government may often rely on the military to assist civilian law enforcement, Congress and the judicial branch tend to frown upon these actions and, depending on the situation, move to prevent that from happening. For example: see Rasul v. Bush.

In a 1946 case related to the implementation of martial law in Hawaii, the Supreme Court said in their ruling:

"Our system of government is the antithesis of total military rule, and its founders are not likely to have contemplated complete military dominance within the limits of a territory made a part of this country."

The debate and tension over when it's appropriate will to use federal or National Guard troops for martial law is unlikely to end.

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