The Insurrection Act of 1807 allows the president to use the military to save the nation.

The Insurrection Act gives U.S. presidents the authority to deploy active duty military to maintain or restore peace in times of crisis. The Insurrection Act was invoked numerous times in the 20th century, most famously when Dwight D. Eisenhower sent the 101st Airborne Division to enforce the desegregation of public schools in Little Rock, Arkansas.

But the origins of the Insurrection Act date back more than 200 years to a bizarre chapter in American history—when Aaron Burr plotted to raise an army and establish his own dynasty in either the Louisiana Territory or Mexico.

Burr, a decorated Revolutionary War officer and senator from New York, served as vice president during Thomas Jefferson’s first term. Burr had grand political aspirations, but they were dashed after he killed his rival Alexander Hamilton in a duel in 1804.

After Duel With Hamilton, Burr Sets Sights on Louisiana

Even though dueling was illegal, Burr was never arrested or tried for Hamilton’s murder, but it effectively ended Burr’s political career. With no prospects in Washington, D.C. or New York, Burr set his sights on the West, namely the newly acquired Louisiana Territory and Mexican-owned lands in the Southwest.

The details of Burr’s plot were never clear, but it involved mustering an army to invade Mexico under the pretense of a war with Spain, and then keeping the conquered land for himself. Burr thought he had an ally in General James Wilkenson, commander of the U.S. Army and first governor of the Louisiana Territory, but when rumors of Burr’s plot leaked into the newspapers, Wilkenson turned on his co-conspirator.

In a letter sent on October 21, 1806, Wilkenson spilled the details of the plot to Jefferson without mentioning Burr by name. But Jefferson had already grown concerned enough about Burr’s strange activities that Jefferson had sent his own letter to Secretary of State James Madison asking if the Constitution granted him authority to deploy the army to stop a rebellion.

www.history.com/news/insurrection-act-thomas-jefferson-aaron-burr