A judge on Tuesday blocked US President Donald Trump's administration from using the military to fight crime in California.

The decision comes as Trump threatened to send troops to more cities, including Chicago.

District Judge Charles Breyer decreed that the Trump administration broke a law known as the Posse Comitatus Act with the deployment of 4,000 National Guard and 700 active duty US Marines to Los Angeles in June of this year.

The legislation limits the deployment of troops for domestic enforcement.

What has the Trump administration planned?

The ruling dealt a setback to the Trump administration's enthusiasm for deploying the military elsewhere in the US.

The White House is likely to appeal the ruling, as spokeswoman Anna Kelly called Breyer a "rogue judge" and said the military deployment had saved Los Angeles from "mass chaos."

"The president is committed to protecting law-abiding citizens, and this will not be the final say on the issue," Kelly said in a statement.

The injunction applies only to the military in California, and is not nationwide.

What did the judge say?

But the judge said that Trump's stated desire to send troops to Chicago and other cities provided support for his ruling, noting that the US president said at an August 27 cabinet meeting that he had the right to "do anything I want to do ... if I think our country is in danger."

Trump has said the troops were needed in Los Angeles to protect federal agents carrying out immigration enforcement, after immigration raids sparked demonstrations.

"There is no question that federal personnel should be able to perform their jobs without fearing for their safety," wrote Breyer, who was nominated to the bench by Democratic President Bill Clinton.

"But to use this as a hook to send military troops alongside federal agents wherever they go proves too much and would frustrate the very purpose of the Posse Comitatus Act."

Trump defiant

Later on Tuesday, Trump told a conservative radio host that federal intervention in Chicago will happen, without stating when.

"I don't want to mention when, but it's going to be happening there. It's going to be happening elsewhere too," Trump said on the "Scott Jennings Radio Show" over whether his administration would be sending federal resources to Chicago this week and whether it would include National Guard troops.

Edited by: Jenipher Camino Gonzalez