Explained | The legal issues surrounding Trump's plan to use troops to suppress protests

Washington: Setting up a rare use of military force on domestic soil, President Donald Trump ordered the Pentagon on Saturday night to send at least 2,000 National Guard troops to respond to protests in Los Angeles set off by his immigration crackdown.

Trump has long mused about using military force on domestic soil to crush violent protests or riots, fight crime, and hunt for immigrants living in the country illegally -- a move that his aides talked him out of during his first term. Between his two presidencies, he said that he would do so without the consent of state governors if he returned to power.

The order is a significant step in that direction, but for now, it stops short of invoking the most expansive power that Trump could claim a right to use. It remains unclear how matters will play out on the ground -- and, potentially, in court.

Here is a closer look at the legal and policy issues.

What did Trump's order do?

Trump called up National Guard troops to be put under federal control. He authorized Defense Secretary Pete Hegseth to use troops to protect immigration enforcement agents, buildings and functions from interference by protesters. As justification, the White House cited recent protests against Immigration and Customs Enforcement raids in Los Angeles.

The order called for the National Guard troops to be deployed for at least 60 days. Trump also authorized Hegseth to use regular federal troops "as necessary" to augment the work of the federalized National Guard units.

The National Guard consists of state-based military forces, largely part-time troops who have separate, full-time civilian jobs. Normally, each state's governor controls its guard and can direct it to deal with a disaster or civil disorder. But under certain circumstances, federal law allows the president to take control of a state's guard.

What will the rules of engagement be?

This is unclear.

Stephen I. Vladeck, a Georgetown University law professor, wrote in a Substack post analyzing the order that for now the federalized troops appeared to have limited authority. Once deployed, they will be able to protect ICE agents and federal buildings against attacks by protesters but not to carry out immigration raids or police the city's streets in general.

But Trump's order did not specify any standards for when troops would be able to use force -- such as arresting people or shooting them -- if his administration deemed a protest to threaten federal personnel, property or functions.

Notably, Hegseth has railed against military lawyers who promoted what he saw as unduly restrictive rules of engagement aimed at protecting civilians in war zones. He has fired the top judge advocate general lawyers who give advice on legal constraints. And his remarks Saturday and Sunday about using troops in Los Angeles have not signaled restraint.

In a social media post, Hegseth called protests against ICE in Los Angeles "violent mob assaults" designed to prevent the removal of immigrants living in the country illegally who he said were engaged in an "invasion."

Hina Shamsi, director of the American Civil Liberties Union National Security Project, said Sunday that "no matter who carries the gun or what uniform they wear, it's important to remember that the Constitution -- and in particular the First Amendment -- applies and troops' conduct is governed by strict constitutional limits."

Is it legal to use federal troops on US soil?

Usually it is not, but sometimes it can be.

Under an 1878 law called the Posse Comitatus Act, it is normally illegal to use federal troops on domestic soil for policing purposes. But an 1807 law, the Insurrection Act, creates an exception to that ban for situations in which the president decides that "unlawful obstructions, combinations or assemblages, or rebellion against the authority of the United States" make it "impracticable" to enforce federal law.

Trump's order criticized the protests as violent and said they threatened to damage federal immigration detention facilities, adding that, "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."

What legal authority did Trump cite?

Trump invoked a statute, Section 12406 of Title 10 of the U.S. Code, that allows him to call National Guard members and units into federal service under certain circumstances, including during a rebellion against the authority of the federal government. But he did not invoke the Insurrection Act.

The call-up statute does not, on its face, confer any authority to use federal troops in the ways Trump authorised Hegseth to use them. But Trump also referred to "the authority vested in me as president by the Constitution," which may mean his administration thinks he can claim inherent power as president to use troops on US soil in those ways.

Notably, during the Vietnam War, William Rehnquist, a future Supreme Court justice, wrote memos for the Justice Department Office of Legal Counsel saying that presidents had inherent power to use troops to prevent anti-war protesters from obstructing federal functions or damaging federal property in Washington, D.C., and at the Pentagon.

Using troops in such a protective capacity would not violate the Posse Comitatus Act, Rehnquist argued as a Justice Department official. But there was no definitive court test of that idea. Moreover, the nation's capital and the campus of the Pentagon are federal enclaves, unlike the businesses in Los Angeles where ICE agents are carrying out raids.

Must a state's governor consent to federal troops?

Not always. But using federal troops on domestic soil outside military bases for policing purposes has happened only in rare and extraordinary circumstances, and doing so over the objection of a state's governor has been even more unusual.

A president last used federal troops for domestic policing purposes in 1992, when President George H.W. Bush invoked the Insurrection Act to suppress widespread rioting that broke out in Los Angeles after a jury acquitted police officers who had been videotaped beating a Black motorist, Rodney King. But in that case, California's governor, Pete Wilson, and Los Angeles' mayor, Tom Bradley, asked for federal assistance in restoring order.

Presidents have not used federal troops without the permission of state governors since the civil rights movement, when Southern governors defied court orders to desegregate public schools.

Notably, during the last presidential campaign, Trump said that if he returned to the White House, he would dispatch military forces into cities such as New York, Chicago, Los Angeles and San Francisco without any request for intervention by local authorities.

"You look at what is happening to our country -- we cannot let it happen any longer," Trump said at a 2023 campaign rally in Iowa. He added: "And one of the other things I'll do -- because you are not supposed to be involved in that, you just have to be asked by the governor or the mayor to come in. The next time, I am not waiting."

Which troops does Trump intend to use?

At least some going into Los Angeles are coming from the California National Guard, but the scope is not clear.

Newsom appears to be assuming that Trump intends to use his state's guard. In a statement Saturday night, Newsom said: "The federal government is moving to take over the California National Guard and deploy 2,000 soldiers. That move is purposefully inflammatory and will only escalate tensions."

And on Sunday, US Northern Command said elements of an infantry brigade combat team from the California National Guard had "begun deploying to the Los Angeles area, with some already on the ground."

But Trump directed Hegseth to "coordinate with the governors of the states" -- plural -- in identifying which units to call into federal service. One possibility that raises is that Hegseth could also send troops from a Republican-controlled state into California, which is Democratic-controlled -- further heightening the political tensions.

Another possibility is that the administration envisions expanding the use of troops to other parts of the country. Notably, Trump's order is not limited to Los Angeles, instead authorizing troops to protect immigration enforcement operations at any "locations where protests against these functions are occurring or are likely to occur."

Hegseth suggested on social media that if he also decided to deploy active-duty troops -- a potential further escalation -- they would most likely be Marines from Camp Pendleton, a major base in Southern California. He said those Marines were already on "high alert."

Will Trump's move be challenged in court?

The chances of litigation challenging the order seem high. But it is early, and little concrete has happened so far. Notably, early Sunday, Trump praised the National Guard on social media "for a job well done," even though no federalized troops were on the ground in Los Angeles yet.

One potential plaintiff is California's government. It would most likely have standing to sue on states' rights grounds and could argue that isolated instances of violence that do not overwhelm the capacity of local law enforcement authorities are not enough to meet legal standards for deploying federal troops.

Newsom's public statements appear to be laying such groundwork. He has said that "there is currently no unmet need" for additional security assistance. He has also urged protesters to stay peaceful and "never use violence" to avoid giving Trump an excuse for a "spectacle," and he called Hegseth's threat to deploy active-duty Marines "deranged behavior."

Section 12406 also says that orders for National Guard call-ups "shall be issued through the governors of the states," which could provide a basis for Newsom to argue that the California National Guard can be federalized under that law only with his concurrence.

There could also be lawsuits on behalf of protesters, invoking individual rights such as First Amendment protections for freedom of speech and assembly. The ACLU drafted potential such lawsuits even before the election as part of contingency planning for what it saw as possible risks from a second Trump administration.