A federal judge in California has barred Border Patrol agents from arresting someone suspected of living in the U.S. illegally unless they have a warrant or a reason to believe the person might flee before a warrant can be obtained.

Border Patrol agents carried out sweeps in California’s Central Valley. Lawyers argued that people were stopped and arrested based on their skin color.

You just can’t walk up to people with brown skin and say give me your papers,’ a federal judge told Border Patrol attorneys at a hearing challenging recent immigration sweeps.