President Donald Trump’s deployment of 2,000 National Guard troops to Los Angeles is stretching the legal limits of how the military can be used to enforce domestic laws on American streets, constitutional law experts say.

Trump, for now, has given the troops a limited mission: protecting federal immigration agents and buildings amid a wave of street protests against the administration’s mass deportation policies. To justify the deployment, Trump cited a provision of federal law that allows the president to use the National Guard to quell domestic unrest.

But Trump’s stated rationale, legal scholars say, appears to be a flimsy and even contrived basis for such a rare and dramatic step. The real purpose, they worry, may be to amass more power over blue states that have resisted Trump’s deportation agenda. And the effect, whether intentional or not, may be to inflame the tension in L.A., potentially leading to a vicious cycle in which Trump calls up even more troops or broadens their mission.

“It does appear to be largely pretextual, or at least motivated more by politics than on-the-ground need,” said Chris Mirasolo, a national security law professor at the University of Houston.

California Gov. Gavin Newsom called the deployment “unlawful” and said he would sue Monday.

“This is about authoritarian tendencies. This is about command and control. This is about power. This is about ego,” Newsom, a Democrat, said Sunday on MSNBC. “This is a consistent pattern.”

At issue is the president’s authority to deploy the military for domestic purposes. A federal law, the Posse Comitatus Act of 1878, generally bars the president from using federal troops — the Army, Navy, Marines, Air Force or Space Force — to enforce domestic laws.

But there are exceptional circumstances when the president can use troops domestically. The most prominent exception is the Insurrection Act, which authorizes the president to deploy the military to suppress insurrections, “domestic violence” or conspiracies that undermine constitutional rights or federal laws. At the end of Trump’s first term, some of his most ardent supporters urged and expected him to invoke the Insurrection Act to push aside state election authorities and essentially void the 2020 presidential election results, although he never did so. During his 2024 campaign, he said he would invoke the act to subdue unrest if reelected.

But so far, Trump has not invoked the Insurrection Act. Instead, in a Saturday order, he cited a different statutory provision: a terse section of the U.S. code that allows the president to use the National Guard — but not any other military forces — to suppress the “danger of a rebellion” or to “execute” federal laws when “regular forces” are unable to do so.

Notably, his order did not outright declare the unrest in L.A. to be a “rebellion,” but suggested it was moving in that direction.

“To the extent that protests or acts of violence directly inhibit the execution of the laws, they constitute a form of rebellion against the authority of the Government of the United States,” the order said.

California authorities and Trump critics say that local law enforcement was effectively managing the L.A. protests. And despite the National Guard’s purportedly defensive role of protecting federal property and personnel, some experts see the deployment as throwing a lit match into a tinderbox.

If the troops are drawn into violent confrontations, Trump might use the clashes as justification for invoking the Insurrection Act, which would pave the way for active-duty military forces to take more aggressive actions to subdue protesters and engage in law enforcement. Defense Secretary Pete Hegseth on Saturday said Marines could be mobilized to L.A. if unrest continues, writing in a post on X that the troops “are on high alert.”

“The laws in this area are somewhat unsettled and untested,” said Rosa Brooks, a Georgetown University law professor who served as a counselor to the undersecretary of defense for policy under President Barack Obama. “Federalizing Guard troops in this situation — and raising the specter of also sending in active duty military personnel — is a political stunt, and a dangerous one.”

Experts are also eyeing whether the Guard members accompany immigration authorities when they venture away from federal buildings — a move that could signal a willingness to use troops to actively aid immigration enforcement, rather than simply protect agents from protesters.

Trump has fueled the fears of further escalation, actively commenting on the protests while attacking the state’s response.

“Looking really bad in L.A.,” he posted early Monday morning, shortly after midnight. “BRING IN THE TROOPS.” He also called for immediate arrests of any protesters wearing masks and repeatedly described them as “insurrectionists.”

However, when asked by reporters Sunday if the violence amounted to an insurrection, Trump said no. 

On Monday, Trump also endorsed the idea of arresting Newsom.

Trump is not the first president to deploy the military over a governor’s objection. But it’s the first time since 1965, when President Lyndon Johnson ordered troops to protect civil rights protesters in Alabama. President Dwight Eisenhower similarly overrode objections from Alabama’s governor, deploying troops to help enforce the desegregation of public schools. When presidents view state and local authorities as being ineffective or recalcitrant, those steps may be justified, some experts say.

“Usually the President calls out the troops with the cooperation of the governor, which happened in LA itself during the Rodney King riots,” said John Yoo, a legal counselor to President George W. Bush. “But there have been times when governors have been tragically slow, as during Hurricane Katrina, or actually resistant to federal policy, as with desegregation, or, arguably, in this case. “

Trump, when speaking about the decision with reporters Sunday, said he warned Newsom a few days earlier of the possibility.

“I did call him the other night,” Trump said. “I said you’ve got to take care of this, otherwise I’m sending in the troops.”

Newsom has railed against Trump’s unilateral action, saying it will inflame rather than ease tensions on the streets and that state and local law enforcement were appropriately responding to the unrest outside federal buildings. Newsom got backup from Democratic governors across the country, who signed a letter calling Trump’s National Guard deployment an “alarming abuse of power.”

“The military appears to be clashing with protesters in the streets of our country. That’s not supposed to happen,” said Elizabeth Goitein, a national security law expert at New York University’s Brennan Center. “It’s such a dangerous situation. It’s dangerous for liberty. It’s dangerous for democracy.”

The promised lawsuit from California will set up yet another high-stakes courtroom test of Trump’s multifaceted bid to expand executive power in his second term.

The last major political fight over the president’s powers to call up the National Guard in an emergency came almost two decades ago, following a decision by President George W. Bush not to activate the National Guard to restore order in New Orleans after Hurricane Katrina. Bush reportedly balked at calling up the National Guard due to the objection of Louisiana Gov. Kathleen Blanco and uncertainty over the legality of the president doing so without her consent.

In response, Congress passed an appropriations rider in 2007that explicitly granted the president that authority during “a natural disaster, epidemic, or other serious public health emergency, terrorist attack or Incident” and in reaction to an “insurrection, domestic violence, unlawful combination, or conspiracy.”

While some legal experts said the measure simply reiterated existing law, an unusually broad coalition — including all 50 U.S. governors — called for repeal of the amendment. And the following year, Congress did repeal it, allowing the law to revert to language in place since the 1950s.