Use of federal troops in Los Angeles is unlawful, judge says

U.S. District Judge Charles Breyer issued the order prohibiting troops.

The Trump administration's use of federal troops in Los Angeles to conduct law enforcement operations is unlawful, a federal judge ruled on Tuesday.

U.S. District Judge Charles Breyer issued an order prohibiting troops from engaging in security patrols, riot control, arrests, searches and crowd control. The order does not take effect until Sept. 12 to allow the Trump administration to appeal.

Breyer said the use of federal troops effectively created a "national police force with the president as its chief" and violated the Posse Comitatus Act.

"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. In short, Defendants violated the Posse Comitatus Act," Breyer wrote.

The 1878 Posse Comitatus Act limits the military from being involved in civilian law enforcement unless Congress approves it or under circumstances "expressly authorized by the Constitution."

One exception is the Insurrection Act, a 218-year-old law signed by President Thomas Jefferson.

The Insurrection Act states, in part: "Whenever there is an insurrection in any State against its government, the President may, upon the request of its legislature or of its governor if the legislature cannot be convened, call into Federal service such of the militia of the other States, in the number requested by that State, and use such of the armed forces, as he considers necessary to suppress the insurrection."

Another provision states it can be used "whenever the President considers that unlawful obstructions, combinations, or assemblages, or rebellion against the authority of the United States, make it impracticable to enforce the laws of the United States in any State by the ordinary course of judicial proceedings."

The ruling on Tuesday sets the stage for a high-profile appeal, as the Trump administration ramps up the use of the federal troops in other U.S. cities, including threats to do so in Chicago.

Breyer issued his decision after holding a three-day trial last month featuring testimony from military leadership about the ongoing operations in the Los Angeles area.

In June, Breyer also ruled President Donald Trump lacked the authority under the Insurrection Act to federalize the National Guard, concluding that the immigration protests in the city failed to meet the criteria of a "rebellion."

ABC News' Alexandra Hutzler contributed to this report.

This is a developing story. Please check back for updates.