The U.S. Department of Justice is suing Maine for denying undercover license plates to federal law enforcement agents, according to a complaint filed Wednesday.

Secretary of State Shenna Bellows, who oversees the Bureau of Motor Vehicles, said in January that the BMV had denied a request from federal border security authorities for confidential, undercover license plates, which came amid rumors about enhanced immigration enforcement in Maine.

Bellows has maintained that the state will not issue unmarked plates to federal agents unless it’s assured they “won’t be used for lawless purposes.”

The DOJ said in a news release Thursday that the state’s decision to withhold the plates threatens effectiveness and safety for federal agents in the Department of Homeland Security, including U.S. Immigration and Customs Enforcement, “who have faced a wave of targeted harassment.”

The federal government also filed similar lawsuits against Massachusetts, Oregon and Washington, the DOJ said.

“By denying undercover license plates to DHS components, including ICE, while issuing them to their own state agencies, these governors are pursuing discriminatory and obstructionist policies against federal law enforcement,” acting U.S. Attorney General Todd Blanche said in a written statement. “These actions undermine federal immigration enforcement, allow dangerous criminals to escape justice and terrorize American communities.”

Bellows said in an interview Thursday that there are legitimate reasons for law enforcement agents to seek confidential plates, but what immigration authorities want to use them for “is something different.”

“They were terrorizing our friends and neighbors, and their mission is civil immigration enforcement,” she said. “We don’t have secret police in Maine.”

Undercover plates are used by federal law enforcement officers, including within DHS, to blend in and “avoid premature detection” while conducting operations, according to the complaint.

Maine paused issuing such plates after a request from U.S. Customs and Border Protection, Bellows said in January, while noting that the state had not revoked any license plates that had already been issued.

The state then updated the application for its confidential plate program, requiring interested agencies to certify that the plates would not be used for civil immigration enforcement.

Bellows said that update doesn’t mean immigration agents working in Maine can’t have any license plates — they can register and receive federal plates that link back to their agency.

“What they can’t do is have a confidential plate that would be untraceable, even for law enforcement in our state,” she said. “That’s what we’re saying no to.”

Bellows’ office said the BMV has approved 48 confidential plates for eight federal agencies since January, but that it has not approved March applications from ICE seeking 11 such plates.

In the complaint, the DOJ accuses Maine of unfairly discriminating against the federal government by refusing to issue plates for vehicles that would be used for civil immigration enforcement.

The federal government also contends that the action increases risk for federal agents “and the communities they serve.”

“When an unmarked vehicle can be traced to a federal agency, the negative consequences for federal law enforcement officers can be immediate,” the complaint reads. “Federal officers rely on confidential plates to investigate, monitor and apprehend targets. They help officers avoid confrontations and evasion by those targets or other members of the public.”

Bellows contends that the community has a right to know if officers are associated with the federal government or ICE.

“This idea of knowing who the authorities are is really fundamental to our democracy,” Bellows said. “If someone is knocking on the door, seeking to arrest someone or detain them for civil violations, they should be identifying themselves.”