The flag of the U.S. state Wisconsin is seen in this illustration taken, August 21, 2024. REUTERS/Dado Ruvic/Illustration

By Nate Raymond

Dec 3 (Reuters) - The Wisconsin Supreme Court on Wednesday agreed to consider whether state law prohibits local jails from detaining individuals at the request of federal immigration authorities—a decision that could complicate President Donald Trump's efforts to ramp up deportations in the state.

The court, which currently has a 4-3 liberal majority, will take up a case the immigrant rights group Voces de la Frontera filed directly with it in September. The lawsuit challenges five county sheriffs’ practice of honoring civil detainer requests from U.S. Immigration and Customs Enforcement.

At least four justices are needed for the court to hear a case filed directly with the justices rather than in the lower courts. The vote breakdown was not disclosed, but conservative Justices Annette Ziegler and Rebecca Bradley publicly dissented from the decision to hear the case.

Justice Brian Hagedorn, a conservative, wrote separately—without revealing his vote—to stress how publicly dissenting from the mere decision to hear a case goes against a "longstanding tradition" on the court, whose practices are evolving with its "newfound fondness" for taking cases on an expedited basis that are often politically charged. He said publicly dissenting at this stage could lead parties to believe "certain justices have settled on a view of the merits prior to briefing."

Timothy Muth, a lawyer for the plaintiff at the American Civil Liberties Union of Wisconsin, in a statement welcomed the court's decision to take up the case. "ICE continues to send hundreds of these detainers to Wisconsin jails, and people throughout the state are being illegally held for days so that ICE can pick them up," he said.

The case targets county sheriffs' offices in Walworth, Brown, Kenosha, Sauk, and Marathon counties. The ACLU of Wisconsin contends that under Wisconsin law, keeping a person detained when they are entitled to be released constitutes a new arrest. It argues that the sheriffs lack authority to hold people pursuant to ICE detainers, because a Wisconsin statute largely bars law enforcement from making arrests for civil actions.

The case is the latest instance of a lawsuit in state court seeking to challenge the ability of state and local authorities to cooperate with ICE and Trump's hardline immigration agenda.

During Trump's first term in office, state high courts in Massachusetts and Montana, as well as state appeals courts in Minnesota and New York ruled that local law enforcement was restricted or barred from holding people based on federal immigration detainers. Those are voluntary requests to local authorities to hold individuals for up to 48 hours past when they are entitled to be released from jail so ICE can take custody of them.

Lawyers for Voces de la Frontera asked Wisconsin's Supreme Court to expedite the case, alleging ICE in the first seven months of 2025 had sent over 700 detainers to local jails, leading to at least 247 people being unlawfully held.

Trump's administration has not weighed in on the case to date. The U.S. Department of Homeland Security, which oversees ICE, did not respond to a request for comment.

The sheriffs in an October brief urged the court to not hear the case, arguing they have long cooperated with ICE and there was no reason to rush the case or bypass the lower courts. They also contended that the state law the plaintiff relies on does not apply when a sheriff cooperates with federal immigration authorities.

Samuel Hall, a lawyer for four of the sheriffs at Crivello, Nichols & Hall, said they were reviewing the court's Wednesday order and evaluating their next steps.

"We are confident, however, that Wisconsin sheriffs who honor ICE detainers do so fully within the bounds of Wisconsin law and the federal legal framework governing immigration enforcement," Hall said in a statement.

The case is Voces de la Frontera v Gerber, Wisconsin Supreme Court, No. 2025AP002121.

For Voces de la Frontera: Timothy Muth of the ACLU of Wisconsin

For the sheriffs: Samuel Hall of Crivello, Nichols & Hall and Andrew Phillips of Attolles Law

(Reporting by Nate Raymond in Boston)