An appeals court has blocked a California law passed in 2025 requiring federal immigration agents to wear a badge or some form of identification.

The Trump administration filed a lawsuit in November challenging the law, arguing it would threaten the safety of officers who are facing harassment, doxing and violence, and that it violated the constitution because the state is directly regulating the federal government.

A three-judge panel of the ninth US circuit court of appeals issued an injunction pending appeal on Wednesday. It had already granted a temporary administrative injunction to block the implementation of the law.

At a hearing 3 March, justice department lawyers argued that the California law sought to regulate the federal government, violating the supremacy clause of the constitution.

The appeals court agreed, saying the law “attempts to directly regulate the United States in its performance of governmental functions”, in an opinion written by Judge Mark J Bennett.

California lawyers argued that the law applied equally to all law enforcement officers without discriminating against the US government, and that states could apply “generally applicable” laws to federal agents. They also argued that the law was important to address public safety concerns.

The initial lawsuit also addressed another California measure signed into law last year that would have banned most law enforcement officers from wearing masks, neck gaiters and other facial coverings. It was blocked by a federal judge in February.

The legislation did not apply to state law enforcement and made exceptions for undercover agents, protective equipment like N95 respirators or tactical gear, and other situations where not wearing a mask would jeopardize the operation.