There are few laws that President Trump tests more often than the Insurrection Act.
The 200-year-old law provides emergency powers to assign active-duty soldiers to civilian police service, which is otherwise prohibited by federal law.
Trump and his team have threatened to use it almost daily for weeks – most recently on Monday after a reporter pressed the president about his escalation of efforts to send federal troops to Democratic-led cities.
“The Insurrection Act, yeah, I mean, I could do that,” Trump said. “Many presidents have done this.”
Roughly a third of US presidents have invoked these laws at some point, but history also shows that the law has only been used in moments of extreme crisis and political upheaval.
The Insurrection Act was Abraham Lincoln's sword against secessionists and Dwight D. Eisenhower's shield around the Little Rock Nine, young black students who pioneered school desegregation in Arkansas.
Ulysses S. Grant used it more than half a dozen times to prevent coups d'etat, stop racial murders, and strangle the Ku Klux Klan in its cradle in South Carolina.
But just as often it was used to suppress worker strikes and stifle protest movements. The last time it was used, Defense Secretary Pete Hegseth was in elementary school and most American soldiers had not yet been born.
Now many fear Trump could use the law to crush opposition to his agenda.
“Democrats were fools for not amending the Insurrection Act in 2021,” said Kevin Carroll, a former senior adviser to the Department of Homeland Security during Trump’s first term. “This gives the president virtually unlimited power.”
This also eliminates most forensic audits.
“You can’t even argue with that,” Trump boasted on Monday. “I don’t have to go there yet because I’m winning my appeal.”
If that winning streak cools, as legal experts say it could soon, some fear the administration's next move will be the Insurrection Act.
“The Insurrection Act is written very broadly, but there is a history of even the executive branch interpreting it narrowly,” said John C. Dehn, an assistant professor at Loyola University Chicago Law School.
The President first proposed using the Insurrection Act against protesters in the summer of 2020. But his Cabinet members and military advisers blocked the move as they sought to use the National Guard for immigration enforcement and the military for border patrol.
“They're really fixated on using the military domestically,” Carroll said. “It's ominous.”
Instead, during his second term, Trump used an obscure subsection of the U.S. code to send federal soldiers into blue cities, arguing that it provided many of the same powers as the Insurrection Act.
Federal judges disagreed. Since then, appeals courts have been clogged with deployment issues in Los Angeles, Portland, Ore., and Chicago, with three West Coast cases pending before the 9th U.S. Circuit Court of Appeals and one pending in the 7th Circuit, which has jurisdiction over Illinois.
The result is a growing knot of litigation that experts say the Supreme Court will have to untangle.
As of Wednesday, troops in Oregon and Illinois have been activated but cannot deploy. The situation in Oregon is further complicated by precedent from California, where federal troopers have been patrolling the streets since June with the blessing of the 9th District. This decision will be reviewed by the district court on October 22 and could be overturned.
Meanwhile, what California soldiers are legally allowed to do while they are federalized is also under review, meaning that even if Trump retains the power to call up troops, he may not be able to use them.
Scholars disagree on how the Supreme Court might rule on any of these issues.
“At this point, no court … has expressed any sympathy for these arguments because they are so weak,” said Harold Hongju Ko, a professor at Yale Law School.
Koh listed the Supreme Court's most conservative members, Clarence Thomas and Samuel A. Alito Jr., as unlikely to resist the president's authority to invoke the Insurrection Act, but said even some of Trump's appointees — Neil M. Gorsuch, Brett M. Kavanaugh and Amy Coney Barrett — might be skeptical, along with the chief justice John G. Roberts Jr.
“I don't think Thomas and Alito are going to stand up to Trump, but I'm not sure Gorsuch, Kavanaugh, Barrett and Roberts can read this statute to give him [those] powers.”
The Insurrection Act bypasses this fight almost entirely.
That “would change not only the legal landscape, but it would fundamentally change the facts that we have on the ground because what the military would be allowed to do would be much broader,” said Christopher Mirasola, an assistant professor at the University of Houston Law Center.
Congress created the Insurrection Act as a credible response to armed mobs attacking their neighbors and organized militias seeking to overthrow elected officials. But experts warn that the military is not trained to maintain law and order, and that the country has a strong tradition against domestic deployments dating back to the Revolutionary War.
“Uniformed military leaders generally don’t like to get involved in domestic law enforcement issues,” Carroll said. “The only similarity between the police and the military is that they have uniforms and weapons.”
Today, the commander in chief can invoke the law in response to a call for help from state leaders, as George H. W. Bush did to quell the Rodney King uprising in Los Angeles in 1992.
The statute can also be used to combat elected officials who refuse to enforce the law, or mobs who make it impossible—something Eisenhower and John F. Kennedy Jr. did in defense of school integration.
However, modern presidents tend to avoid using the Insurrection Act even in circumstances with strong legal justification. George W. Bush considered implementing the law after Hurricane Katrina caused chaos in New Orleans, but ultimately decided against it over concerns that it would intensify an already bitter power struggle between the state and federal governments.
“There are a lot of internal Justice Department opinions where attorneys general like Robert Kennedy or Nicholas Katzenbach said, 'We can't invoke the Insurrection Act because the courts are open,'” Koch said.
Despite its extraordinary power, Koch and other experts say the law has hurdles that would make it harder for the president to enforce it in the face of naked cyclists or protesters in inflatable frog suits, which federal forces recently encountered in Portland.
“There are still legal requirements that need to be met,” said Dehn, the Loyola professor. “The problem the Trump administration would face if it invoked [the law] it's very practical they are to be able to arrest people who break the law and prosecute people who break the law.”
This may be why Trump and his administration have yet to implement this law.
“It reminds me of the build-up to Jan. 6,” Carroll said. “It's a similar feeling that people have: the feeling that an illegal, immoral and unreasonable order is about to be given.”
He and others say invoking the Insurrection Act would push widespread concerns about military policing America's streets into existential territory.
“If there is a bad faith use of the Insurrection Act to send in federal troops to beat up anti-ICE protesters, there should be a general strike in the United States,” Carroll said. “This is a real glass-breaking moment.”
At this point, the best protection may come from the military.
“If a truly unwise and immoral order comes out … 17-year-old generals should say no,” Carroll said. “They have to have the courage to put their stars on the table.”
