A federal judge in San Francisco seemed unconvinced after a three-day trial that the continued deployment of federalized members of California’s National Guard — who were originally deployed to Los Angeles in response to protests against President Donald Trump’s immigration agenda — is lawful.

US District Judge Charles Breyer specifically questioned Justice Department attorneys on Wednesday on the issue of what limits exist to regulate the use of federal law enforcement to protect federal buildings and employees, as the DOJ alleges is the case with the nearly 300 remaining troops on the ground in California.

“Once you have a force in place, and maybe legitimately do so, and the threat that gave rise to the force in that place subsides, or is no longer of serious concern, what then?” Breyer asked a Justice Department attorney on Wednesday. “How does one look at this national police force, which goes out of where the threat was and starts executing other laws?”

The comments from Breyer came on the final day of a three-day bench trial about how several thousand members of California’s National Guard were used after Trump federalized them in June as dramatic protests unfolded in Los Angeles.