The Constitution gives Congress power to call forth the militia to execute the laws, suppress insurrections, and repel invasions, and to organize and arm it, while leaving the states the appointment of officers and training. The modern Guard took shape with the Militia Act of 1903 and later laws that made Guard members part of the federal reserve forces. Today Guard units respond to hurricanes and floods at home and deploy to combat zones abroad.
This guide explains how the Guard is organized, who commands it, what it does, and the debates over its domestic use.
Supporters of the deployments argue that Presidents must be able to protect federal officers and property and enforce federal law when local officials will not, and that the Guard deters violence. Critics, including governors of both parties, argue that federalizing Guard troops over governors' objections undermines state authority and that using soldiers in domestic policing threatens civil liberties. Congress has considered bills to clarify the Insurrection Act and limit Title 10 call-ups, while the courts continue to define the limits.
On state active duty, Guard members are commanded and paid by the governor under state law. Under Title 32 of the U.S. Code, they remain under the governor's command but are paid by the federal government for federally approved missions, such as border support or pandemic response, and can perform law enforcement. Under Title 10, they are federalized, commanded by the President through the military chain of command, and generally barred from law enforcement by the Posse Comitatus Act. The National Guard Bureau, whose chief sits on the Joint Chiefs of Staff, coordinates between the states and the Pentagon.
In June 2025 the President federalized California Guard troops under a law allowing call-ups when the President cannot execute federal law with regular forces, sending them to Los Angeles over the governor's objection to protect federal property and personnel during immigration protests. Later deployments followed in Washington, D.C., where the President commands the Guard, and in other cities including Portland and Chicago, prompting lawsuits by states. On December 23, 2025, in Trump v. Illinois, the Supreme Court refused to allow the Illinois deployment, finding the government had not identified authority for the military to execute the laws there.
Guard units have fought in every major American war since the Civil War, and after the September 11 attacks hundreds of thousands of Guard members deployed to Iraq and Afghanistan, at times making up a large share of forces there. In Perpich v. Department of Defense in 1990, the Supreme Court held that governors cannot block federal orders sending their Guard units abroad for training. Frequent deployments have strained Guard members, their families, and employers, who are protected by federal reemployment law.
Governors call out the Guard for hurricanes, floods, wildfires, blizzards, and civil unrest, and states share Guard units through an interstate mutual aid compact. Guard members supported COVID-19 testing and vaccination, border security operations, and security for presidential inaugurations. Famous domestic deployments include President Eisenhower's federalization of the Arkansas Guard in 1957 to enforce school desegregation in Little Rock and the deadly shooting of students by Ohio Guard troops at Kent State in 1970.
The Guard traces its origins to the Massachusetts Bay Colony militia regiments of 1636. The Constitution's militia clauses divided control between Congress and the states, and for more than a century state militias varied widely in quality. The Militia Act of 1903 created the modern National Guard with federal funding and standards, and the National Defense Act of 1916 and a 1933 law made Guard members part of the Army's reserve. The Air National Guard was created in 1947.
See the full military structure in the military chain of command, learn about emergency authorities in emergency powers explained, or see the 2025 capital deployment in the D.C. statehood debate.