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This Expert Brief combines responses to questions posed to Matthew C. Waxman, adjunct senior fellow for law and foreign policy, and Peter Mansoor, CFR member and General Ramond E. Mason Jr. military history chair at Ohio State University. Waxman previously served in the U.S. State Department and the National Security Council. Mansoor was a former U.S. Army Colonel who commanded the First Brigade of the First Armored Division in Iraq from 2003 to 2005.
On June 6, 2025, Immigration and Customs Enforcement (ICE) agents carried out mass raids arresting unauthorized immigrants across Los Angeles and Southern California. The arrests sparked protests outside a federal courthouse in LA. In response, President Donald Trump signed a memorandum authorizing the deployment of at least two thousand National Guard members to protect ICE and federal property. On June 13, about two hundred U.S. Marines arrived in the city to support the National Guard at the president’s order.
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California Governor Gavin Newsom sued the administration that same day for “unlawfully” bypassing his permission to deploy federal troops to the state after a formal request that the Trump administration retract its troop deployment was ignored. District Judge Charles Breyer, the federal judge on the case, rejected Trump’s rationale for federalizing the troops and ordered the president to relinquish control of the California National Guard. However, a federal appeals court paused Judge Breyer’s ruling to consider the Trump administration’s appeal, allowing the National Guard to remain in LA. Judge Breyer did not rule on the legality of deploying Marines in the state.
What is the Trump administration’s legal justification for deploying the National Guard and U.S. Marines to Los Angeles?
MATTHEW C. WAXMAN: The president has declared that he is sending in federalized National Guard troops and other military personnel, pursuant to a combination of his constitutional and statutory powers, to protect federal personnel and federal government facilities. The essence of his claim is that violent protests threaten these federal instrumentalities and that California state authorities lack the ability or will to protect against those threats.
PETER MANSOOR: The Trump administration is using the justification of deploying troops to protect federal property, which is a legal reason. But then they go beyond this in their political statements to say that they’re suppressing riots, which is not in the remit of federal forces. The Posse Comitatus Act prevents federal forces from intervening in civilian law enforcement matters within the United States. By deploying the National Guard, in a federalized capacity, and active-duty Marines, the Trump administration is making a political statement that it is tough on crime and that the demonstrations in Los Angeles are a danger to the nation—which is not true.
How did Trump federalize the National Guard?
MANSOOR: This is an interesting question because the National Guard actually has more authorities when operating under the state governor’s control under Title 32. They can be used in a law enforcement capacity, in that regard. Once they’re federalized by the president, then they fall under federal statutes, and again, the Posse Comitatus Act then applies. By federalizing them, the National Guard has less capacity to intervene in riots and law enforcement matters than they would under a governor’s control.
Of course, this is the whole point, because Governor Newsom wasn’t about to use the National Guard—there was no need for it. Increased police presence was getting the situation under control, but federalizing the National Guard was the only way that President Trump was going to be able to insert large numbers of military troops into the situation.
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What is the significance of District Judge Breyer’s ruling?
WAXMAN: Among other things, the judge ruled that the president lacked authority to deploy the California National Guard because the situation in Los Angeles did not amount to any real danger of ‘rebellion.’ The opinion essentially suggests violence or threatened violence beyond a certain threshold were not met and that the president’s move violated the state’s constitutional prerogatives.
I was surprised by the ruling, and I think there’s a good chance that it will be reversed on appeal. I say so not because I think the president’s use of the National Guard was needed or wise but because the statute is drafted very broadly and courts usually give very strong deference to the president's assessments of these matters.
Is the Insurrection Act involved, and what is Title 10 of the U.S. Code?
WAXMAN: So far, the president has not taken the next big step of invoking the Insurrection Act. Doing so would probably put these military forces in the role of directly enforcing law. That would cross a very serious line, especially if California state officials continue to say that they object to the military role.
MANSOOR: Title 10 is the code under which U.S. military forces operate. The Insurrection Act was enacted in 1807 after a potential insurrection by Aaron Burr, vice president at the time, who had killed his opponent, Alexander Hamilton, in a duel. He was thinking about launching an insurrection against the United States president. President Thomas Jefferson then convinced Congress to establish a law that would allow U.S. military forces to be used in a civil law enforcement capacity in order to put down insurrections against the United States.
Has the U.S. military been deployed against American citizens before?
MANSOOR: There’s definitely precedent for the deployment of federal forces in law enforcement issues. President Dwight D. Eisenhower used federal troops, the 101st Airborne Division, to ensure the desegregation of Little Rock High School in Arkansas back in the 1950s. In 1967, federal troops were deployed to Detroit when the city was subject to massive riots.
Then, in 1992 during the Rodney King riots in Los Angeles, California Governor Pete Wilson requested help from the president. President George H.W. Bush deployed the 7th Infantry Division and other forces to Los Angeles and federalized the National Guard there, as well as invoked the Insurrection Act to allow those troops to be used in a law enforcement capacity, and they were able to quell the riots that had engulfed the city.
When would federal troops be called in to handle state matters of law enforcement, and has law enforcement been insufficient in handling the recent protests in LA?
MANSOOR: So, this is really up to the governor. If the governor feels that they can’t control the violence in one of their cities, the governor can request help from the federal government. But law enforcement is localized in this country, and then after that, it’s a state matter. It very rarely is a federal issue because of all the implications that come with deploying active-duty troops that aren’t exceptionally well trained for law enforcement matters. Active-duty forces should be used sparingly and only as a last resort. And we're far from that in the case of what’s happening in Los Angeles today.
These demonstrations in Los Angeles today are not overly violent. What violence there is has been confined to a very small area. This is a police matter, and yet the president wants to make a political statement, not necessarily because security demands a military presence.
What effect could the deployment of military troops on U.S. civilians have on the country’s civil-military relations?
MANSOOR: For many years, if not decades, the military has been one of the most revered institutions in the United States, with large-scale and widespread public backing. If you use the military in the sorts of capacities that the Trump administration wants to use them for, it jeopardizes this relationship with the American people, and then the civil-military relationship deteriorates.
WAXMAN: Keep in mind that this has been a delicate constitutional issue since the birth of the republic. It was a sensitive issue in the drafting of the Constitution and it has remained a sensitive issue ever since.
What are the risks of a federalized response causing protests to spread and potentially lead to new deployments?
WAXMAN: Quelling violence is always difficult, and even when militarized responses are justified, there are of course risks of escalation. That’s true at home as well as abroad, so especially when military forces are deployed to deal with domestic crises, proper training, rules of engagement, and planning are critical. It’s also a reason that collaboration between federal and state governments is usually important.
MANSOOR: The federalized response to riots in Los Angeles will inspire demonstrations in other cities, not just against ICE and its tactics, but against the use of military forces in civilian law enforcement. If those demonstrations turn violent, they could lure the president to use military forces elsewhere within the United States—creating a dangerous feedback loop with a very uncertain ending.
This interview has been edited for length and clarity. This work represents the views and opinions solely of the authors. The Council on Foreign Relations is an independent, nonpartisan membership organization, think tank, and publisher, and takes no institutional positions on matters of policy.
This Expert Brief was compiled and edited by Clara Fong.