As protesters and federal law enforcement clashed in Minneapolis in the wake of a second shooting of a civilian on Jan. 14, 2026 by federal agents, President Donald Trump threatened to invoke the Insurrection Act to send troops to Minnesota in response to protests.

This is not the first time Trump has invoked the act.

Is Trump’s warning just bluster? Does the president have the authority to send the military into American cities?

The answer to this question involves a web of legal provisions that help define the president’s constitutional roles as commander in chief and chief executive of the country and that simultaneously try to balance presidential power with the power of state leaders.

Tracing back to the Magna Carta, the British charter of liberty signed in 1215, there is a longstanding tradition against military involvement in civilian affairs.

However, the U.S. Constitution guarantees that the national government will protect the states in times of violence and permits Congress to enact laws that enable the military to aid in carrying out the law.

Almost immediately after the Constitution’s enactment in 1787, Congress passed a law that allowed the president to use the military to respond to a series of citizen rebellions.

Troops serving as what’s called “posse comitatus,” which translates roughly to “attendants with the capacity to act,” could be called to suppress insurrections and help carry out federal laws.

Following the Civil War, the national government used troops in this capacity

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