U.S. President Donald Trump has threatened to invoke the Insurrection Act, which has not been utilized by a U.S. president in more than three decades.
Trump has signalled an eagerness to send the military to several U.S. cities, mostly led by elected officials from the Democratic Party, to quell what he and others in his administration have characterized as out-of-control crime.
So far, legal battles are playing out between the Trump administration and officials in Illinois, California and Oregon, who have not solicited or welcomed the federal intervention. But the president could try to take a more authoritative approach to doing so.
"If I had to enact it, I'd do that," he said on Monday. "If people were being killed and courts were holding us up or governors or mayors were holding us up, sure, I'd do that. I mean, I want to make sure that people aren't killed. We have to make sure that our cities are safe."
Here's a look at the history and the controversies surrounding declaring an insurrection.
What is the Insurrection Act?The Insurrection Act gives the U.S. president the power to deploy the military or federalize National Guard troops inside to stop uprisings and rebellions.
While, the law is commonly referred to as the Insurrection Act of 1807 because that was the year then-president Thomas Jefferson signed it into law, experts like Stephen Vladeck, a law professor at Georgetown University, have pointed out in recent weeks that the role of the military in domestic law enforcement is outlined not in just one act but in a series of statutes passed from the late 18th century to 1871.
WATCH | Legal battle over troop deployment to Portland continues:A U.S. federal judge has temporarily blocked the Trump administration from deploying any National Guard units to Oregon, including the California National Guard. The State of Illinois and the City of Chicago have also sued the Trump administration over its effort to deploy National Guard troops to that state.The Insurrection Act can essentially override the Posse Comitatus Act, passed in 1878. That law generally bars the federal branches of the military from engaging in the law enforcement, responsibilities that rest with local authorities.
Under the invocation of the Insurrection Act, troops can perform searches or make arrests.
When Trump sent the National Guard to Los Angeles and other cities this past summer, he relied on a different legal basis, Section 12406 of Title 10 of the U.S. Code.
That section prohibits the National Guard from carrying out civilian law enforcement activities. This means that they can help protect federal officers and property but are not allowed to conduct arrests. Democrats and critics of the administration have derided images of military members collecting trash and performing other ordinary tasks.
Why is it controversial?There is a long American tradition of keeping the federal military out of civilian affairs.
The nation's founders, having witnessed abuses by the British military during colonial times, feared that giving the president unlimited control over troops would erode civil liberties, constitutional scholars have said.
There is also the matter of the statutes themselves, some of which have been characterized as overly broad or vague.
"Nothing in the text of the Insurrection Act defines 'insurrection,' 'rebellion, domestic violence,' or any of the other key terms used in setting forth the prerequisites for deployment," Joseph Nunn, a historian of military law, wrote in 2022 for the liberal non-profit Brennan Center for Justice.
Section 253 of the Insurrection Act is particularly problematic, Laura A. Dickinson, a law professor at George Washington University, wrote last year.
The section could be interpreted to "encompass even relatively minor obstructions to the 'execution of the laws' of the United States or impediments to 'the course of justice' under those laws, such as a small protest interfering with law enforcement activities or judicial proceedings, so long as there were a conspiracy to do so by two or more persons," Dickinson wrote for the non-profit website Lawfare.
How are the states reacting?Historically, in instances where the Insurrection Act was invoked, presidents and governors have usually agreed on the need for troops.
In 2005, then-president George W. Bush decided not to invoke the Insurrection Act to send active-duty troops to Louisiana in the aftermath of Hurricane Katrina, in part because the state's governor opposed the move.
Local officials are voicing their displeasure in 2025, as well.
"In America we don't put the military on our streets unless it's extreme circumstances, like an invasion or a rebellion, and those things, they just don't exist right now in Oregon," the state's attorney general, Dan Rayfield, told NBC News on Sunday, speaking about conditions in Portland.
Illinois Gov. J.B. Pritzker, seen on Aug. 3, is among the state and municipal officials criticizing Trump's move to send the military to Chicago and other U.S. cities. (Tom Krawczyk/Reuters)Illinois Gov. J.B. Pritzker said this week it was his view that the Trump administration's goal is to "make it seem that peaceful protesters are a mob by firing gas pellets and tear gas canisters at them ... to create the pretext for invoking the Insurrection Act."
While American cities have much higher rates of violent crime than cities in other Western countries, in general in the U.S., per-capita homicide rates have fallen in recent years from heights seen between the 1970s and 1990s — aside from a pandemic bump in some cities between 2020 and 2023.
Chicago officials, for example, have recently said there were fewer homicides in the city this past summer than in any year since 1965. Chicago tallied 525 homicides last year, the city's police department reports, far below the early 1990s, when the number was often above 900 per year.
When has the act been used before?The Insurrection Act has been invoked about 30 times since its inception, but the last president to do so was George H.W. Bush in 1992, acting at the request of Pete Wilson, the governor of California.
That request came after riots and several acts of arson were committed in Los Angeles following the acquittal of four police officers in connection with the beating of a civilian, Rodney King, which had been captured on amateur video the previous year.
A fire is shown burning out of control in South Central Los Angeles in this April 30, 1992 photo, after police officers were acquitted in the assault case of Rodney King. The riots led to the last use of the Insurrection Act. (Paul Sakuma/The Associated Press)The days-long protests resulted in an estimated $1 billion US in damages and over 60 deaths, several of which remain unsolved crimes to this day. Another 2,000 people were injured and 6,000 were arrested.
When he was president, Lyndon Johnson invoked the act in a similar fashion in 1967, after riots broke out in African American neighbourhoods in Detroit over police tactics.
Johnson was one of three presidents, along with Dwight Eisenhower and John F. Kennedy, who invoked the act in specific cases to protect the rights and safety of civil rights protesters or Black students attending schools in the southern U.S.
The most famous use of the act historically may have been when Abraham Lincoln invoked it in 1861 as several southern states seceded.
Would Trump be prevented legally?Joseph Nunn, writing for the Brennan Center, said an 1827 case set the parameters for a president to have exclusive authority to decide when the military can be deployed.
But, he wrote, in subsequent cases, "the Supreme Court has suggested that courts may step in if the president acts in bad faith, exceeds 'a permitted range of honest judgment,' or acts in a way manifestly unauthorized by law.
However, the current U.S. Supreme Court has given Trump wide latitude in unsigned orders this year where he has exercised authority, including on deportations and widespread dismissals of federal government officials. The court has a 6-3 tilt of conservative justices, three appointed by Trump in his first term.