WASHINGTON

A federal judge in California ruled on Tuesday that US President Donald Trump's controversial deployment of the National Guard and Marines to quell protests in Los Angeles is illegal.

District Court Judge Charles Breyer issued an injunction blocking the military from being used for policing, but did not require the troops to be withdrawn from California. He found that the president violated a long-standing law known as the Posse Comitatus Act. The 1878 law generally bars the military from being used for civilian law enforcement.

Breyer flatly rejected Trump and his senior officials' rationale for deploying the military, saying there was neither a rebellion taking place in Los Angeles as demonstrators railed against the president's immigration crackdown, nor was domestic law enforcement incapable of dealing with the unrest.

"The evidence at trial established that Defendants systematically used armed soldiers (whose identity was often obscured by protective armor) and military vehicles to set up protective perimeters and traffic blockades, engage in crowd control, and otherwise demonstrate a military presence in and around Los Angeles," Breyer wrote.

"In short, Defendants violated the Posse Comitatus Act," he added.

Breyer pointed to statements from Trump in which he indicated he wanted to emulate the model he developed in Los Angeles in other major cities, saying the president is "creating a national police force with the President as its chief," and said there is "an ongoing risk that Defendants will act unlawfully" as he issued his injunction.

The suit was brought by California Gov. Gavin Newsom, who had argued that Trump's use of the military to respond to mass demonstrations was illegal.

"A federal court granted our injunction, blocking Trump’s illegal use of the military for domestic law enforcement. The ruling is clear: Trump is breaking the law by trying to create a national police force with himself as its chief," Newsom said on X, quoting the ruling.

There are roughly 300 US troops who remain in Los Angeles after Trump first deployed them to America's second-largest city in June, and Breyer order the Trump administration to stop using them for "arrests, apprehensions, searches, seizures, security patrols, traffic control, crowd control, riot control, evidence collection, interrogation, or acting as informants" unless the Posse Comitatus Act can be lawfully invoked.

The Trump administration is highly likely to appeal the ruling. Breyer delayed his injunction from taking effect until Sept. 12.