In January, Border Patrol agents conducted sweeps through immigrant communities in California’s Central Valley, arresting nearly 80 individuals the agency said were unlawfully present in the United States.
Officials said the operation, named “Return to Sender,” was intended to target undocumented immigrants with serious criminal backgrounds. But lawyers for those arrested argued that the agents had simply rounded up people who appeared to be day laborers and farm workers, regardless of their actual immigration status, without having a legally sound reason to suspect they were in the country illegally.
On Tuesday, a federal judge in California issued a preliminary injunction barring Border Patrol agents from stopping individuals without having a reasonable suspicion of illegal presence, as required by the Fourth Amendment.
The judge also blocked agents from making warrantless arrests unless they have probable cause to believe the person is likely to flee before a warrant can be obtained.
The Trump administration has adopted increasingly aggressive tactics in pursuit of its goal of mass deportations, but has faced pushback from the judiciary. The California ruling marks the latest attempt by courts to rein in enforcement actions that appear to conflict with long-established constitutional and legal protections.
Judge Jennifer L. Thurston of the U.S. District Court for the Eastern District of California noted in her ruling that the government did not “dispute or rebut” the “significant anecdotal evidence” from the plaintiffs regarding Border Patrol’s stop-and-arrest practices.
The preliminary injunction, which applies to the federal district where the sweeps occurred, will remain in place as the case proceeds. A scheduling conference is planned for early June.
The Department of Homeland Security and Customs and Border Protection did not immediately respond to a request for comment.
Representatives for the plaintiffs praised the decision. “You cannot stop people based on how they look,” said Elizabeth Strater, a national vice president of United Farm Workers, a labor union. “This ruling upholds the basic standards of law in the country.”
The Border Patrol operation, carried out in Kern County, which includes Bakersfield, Calif., targeted areas heavily reliant on immigrant labor for agriculture. Agents monitored places including a Home Depot and gas stations frequented by undocumented people.
Gregory K. Bovino, a Border Patrol chief in Southern California, described the operation at the time as an “overwhelming success.” He said in a series of social media posts that it had resulted in the arrests of 78 people who were in the country illegally, including a handful with “serious criminal histories.”
Advocates for farmworkers, however, said that many of those detained had no criminal records and that the raids had terrorized immigrant communities.
In February, lawyers for the American Civil Liberties Union filed a lawsuit against the federal government on behalf of United Farm Workers and five Kern County residents, claiming that Border Patrol agents stopped and arrested individuals regardless of their immigration status or individual circumstances.
The order granting the preliminary injunction cited public data from Border Patrol stating that of the 78 people arrested during the operation, 77 did not have a criminal or immigration history that was known before their arrest.
Steve Eder and Miriam Jordan contributed reporting.
