What Is Martial Law? Who Declares Martial Law?

Martial law is the temporary substitution of military authority for civilian government in an emergency. In the United States, government officials have invoked martial law during war, labor disputes, natural disasters, and in times of civil unrest.

Who Can Declare Martial Law?

Historically, state governors are most likely to declare martial law in cities and counties in their jurisdictions. The federal government’s authority to invoke martial law is less settled and has been used sparingly.

The Federal Government

The United States Constitution doesn’t explicitly mention martial law. No federal statute or U.S. Supreme Court decision clearly states who has the authority to declare martial law and under what circumstances.

Constitutional law scholars who study executive power and the origin of martial law note that the President is the commander in chief of the military. (U.S. Const., art. II, § 2.) But the Posse Comitatus Act prohibits anyone from using federal military personnel for civilian law enforcement, except when expressly authorized by Congress. (18 U.S.C. § 1385 (2026).)

While lacking the authority to unilaterally declare martial law, under the Insurrection Act, the President has limited authority to deploy troops to suppress a domestic rebellion and enforce federal law. (10 U.S.C. §§ 251-253 (2026).) But federal troops deployed pursuant to the Insurrection Act are a supplement to civilian government, not a replacement. President John F. Kennedy invoked the Insurrection Act in 1962 and 1963 to send federal troops to Mississippi and Alabama to enforce civil rights laws.

State Governments

The U.S. Supreme Court has explicitly held that individual states have the power to declare martial law within their borders. Typically, a governor's power to declare martial law originates in the state’s constitution.

But even under martial law, state officials must comply with the U.S. Constitution and federal laws. Federal courts generally won’t second-guess whether a state governor’s declaration of martial law is necessary, but they will review whether state actions taken under martial law are constitutional.

Rather than resort to martial law, most states rely on emergency or police powers to protect public safety and quell civil unrest.

What Happens When Martial Law Is in Effect?

Under martial law, military leaders assume executive, legislative, and judicial powers. When martial law is in effect, military leaders might:

• impose curfews and media blackouts
• suspend the writ of habeas corpus
• commandeer businesses
• prohibit certain sales (like alcohol)
• control hospitals and emergency facilities
• regulate wages and working conditions, and
• require mandatory fingerprinting and identification of civilians.

Civilians who commit crimes or violate military orders face military tribunals if civilian courts are unavailable. For more information about what life is like for civilians under military law, check out: After Pearl Harbor, Hawaii Spent Three Years Under Martial Law.

Martial Law vs. Insurrection Act: Key Differences

The defining feature of martial law is the displacement of the civilian government by the military. When martial law is in effect, military commanders, not elected officials, make laws; soldiers, not local police, enforce laws; and ordinary citizens accused of defying martial law might face military tribunals instead of civilian courts. Civilian governments rarely invoke martial law. Since the United States was founded in 1776, government officials have declared martial law roughly 68 times.

The Insurrection Act is a federal law that allows the president to deploy military forces inside the United States to suppress rebellion, domestic violence, or enforce federal law under specific circumstances. The law is the primary exception to the Posse Comitatus Act, which generally prohibits federal military involvement in civilian law enforcement. Unlike martial law, the Insurrection Act does not authorize the military to replace the civilian government. For example, Presidents Dwight D. Eisenhower and John F. Kennedy invoked the Insurrection Act in the 1950s and 1960s to deploy federal troops to enforce school desegregation orders in the South. The troops enforced federal civil rights laws while state and local governments continued operating. The most recent use of the Insurrection Act was in 1992 when President George H.W. Bush deployed troops to Los Angeles during riots following the Rodney King verdict.

What Is the Role of the National Guard?

Government officials sometimes “Call in the National Guard” during civil unrest and natural disasters. In 2020, state governors deployed the National Guard to gatherings that protested police violence and to assist with COVID-19 relief.

Each state and the District of Columbia has its own National Guard, staffed by civilians who serve on a part-time basis. Most of the time, the National Guard is under state control. State governors can activate the National Guard during local or statewide emergencies like hurricanes, protests, and riots.

Under the Insurrection Act, the President can call upon (or “federalize”) the National Guard to suppress a domestic rebellion or enforce federal laws. The President can also deploy National Guard troops overseas. The National Guard has supported more than 1.1 million overseas deployments since the September 11, 2001, attacks on the United States.

Mobilizing the National Guard is not a declaration of martial law. The National Guard serves as a backup, not a replacement, for civilian government. When a state governor deploys National Guard troops to assist with fires, the troops are under the command of local fire marshals. National Guard troops deployed to protests typically work under incident commanders of the local or state police.

National Guard members are required to attend one drill weekend each month and an annual training period (usually 2 weeks in the summer). Members work regular civilian jobs or attend school when they aren’t deployed on missions.

Martial Law and Your Rights

Government officials can invoke martial law under limited circumstances, but checks and balances remain. Contact a lawyer if you have questions about your rights under martial law.

If you are facing criminal charges, you should speak with a criminal defense attorney. If you want to know whether you have a viable claim against the government for a violation of your rights, consider consulting a civil rights attorney.