A federal judge has ruled that US President Donald Trump’s use of National Guard troops during immigration enforcement protests in Southern California violated federal law. US District Judge Charles Breyer, sitting in San Francisco, issued the ruling, finding that the administration overstepped legal boundaries by deploying troops to the Los Angeles area over the summer. While Breyer stopped short of ordering the immediate withdrawal of troops, his decision will take effect Friday.

The ruling stemmed from a lawsuit filed by California, which argued that the deployment breached the Posse Comitatus Act, a law prohibiting the military from carrying out domestic law enforcement duties. State officials claimed the Trump administration had effectively turned soldiers into immigration police. Trump’s lawyers argued the law didn’t apply because the Guard was there only to protect federal agents, not make arrests. They maintained the president had authority to mobilize the troops under separate statutes that grant broad powers for national security. The decision lands as Trump continues to push for military deployments in Democratic-led cities such as Chicago, Baltimore, and New York, echoing his high-profile use of the National Guard in Washington, D.C., where he has direct control. California officials hailed the ruling as a victory for constitutional limits. “The military is not a political tool,” one state attorney said after the decision.