Wisconsin Court Threatens To Obstruct Immigration Enforcement

Wisconsin has two sanctuary cities: Madison and Milwaukee. Officials in those jurisdictions won’t cooperate with ICE. Now Wisconsin could become a sanctuary state due to a new case pending at the Wisconsin Supreme Court.

Contrary to media images of ICE agents rounding up illegal immigrants on street corners, most deportations originate with local law enforcement. A person is arrested on state charges (drunk driving, domestic abuse, or sex assault, for example) and then booked into the county jail. In Wisconsin, like most states, county jails are run by sheriffs.

If the criminal is an illegal alien, and ICE learns of the arrest, then the agency will send the sheriff an “immigration detainer,” also known as an “ICE hold.” These detainers ask the sheriff to hold the alien for up to 48 hours after release from the state charges so that ICE has time to arrange for pickup.

Some sheriffs formalize their relationship with ICE through something called a 287(g) agreement. This is a federal agreement whereby the jail automatically checks all names booked into the jail against the federal ICE database. When there is a hit, ICE sends a detainer, which is honored. In exchange, ICE gives the local agencies grants, equipment, training, and other benefits. There are 13 counties in Wisconsin with these agreements. But whether an agreement exists or not, nearly all Wisconsin counties cooperate with ICE and honor detainers (except for the two sanctuary aforementioned two cities).

ICE detainers are common in Wisconsin. According to one estimate, there were 1,065 holds issued to Wisconsin jails in the first five months of 2025. Ironically, Wisconsin’s Democratic Gov. Tony Evers actually has a policy mandating that the state Department of Corrections comply with ICE holds. So as far as Gov. Evers is concerned, ICE detainers are just fine for those illegal immigrants held in state prisons.

The New Case

Earlier this month, the Wisconsin Supreme Court decided to hear a new case, Voces de la Frontera v. Gerber. The question presented is whether Wisconsin sheriffs have the power under Wisconsin state law to honor immigration detainers.

The petitioners’ main argument is that sheriffs do not have the power to arrest for civil infractions, and because immigration detainers are essentially a civil process, these detentions exceed the powers of sheriffs.

The argument is not as straightforward as the petitioners would like. First, ICE detainers come with administrative arrest warrants. And so a sheriff honoring a detainer is agreeing to exercise delegated federal power and hold that alien pursuant to federal law. This is simply a federal-state agreement, which is a common feature of modern law enforcement. In fact, Wisconsin sheriffs have independent legal authority under state law to enter into cooperative agreements with federal agencies — they do it all the time. If the Wisconsin Supreme Court holds that sheriffs have no power to honor federal warrants, and as a consequence no power to enter into agreements with federal partners, then that holding would jeopardize many existing relationships between state and federal agencies (and the funding that comes with it).

Second, sheriffs have authority to hold individuals based on probable cause that a crime has been committed. Illegal aliens, by virtue of their unlawful presence in the United States, likely violated 8 U.S.C. § 1325. It is a crime to enter the United States without permission. An alien’s unlawful presence is probable cause that a crime has been committed. Additionally, under 8 U.S.C. § 1226, illegal aliens who violate state criminal laws are considered “criminal aliens” under federal law. And any alien in the United States who is undocumented has failed to register, which is a crime in violation of 8 U.S.C. § 1302. ICE, in fact, could likely clear up much of this legal argument by simply telling sheriffs that probable cause exists that the alien violated federal criminal law.

Leftist Tactic in Other States

The fact that the court granted this request is a sign that it wants to grant the relief requested by petitioners. They could have allowed this case to percolate in the lower court, ironing out all the complicated factual issues presented by the federal policy. But they didn’t. The Wisconsin Supreme Court is in the firm grip of a 4-3 liberal majority.

This lawsuit is the latest part of a nationwide strategy. Similar lawsuits have been filed and succeeded elsewhere, such as Minnesota, New York, Montana, Massachusetts, and Colorado. These lawsuits used the same tactic: getting a left-leaning court to declare that state law prohibits state cooperation with ICE detainers.

Impending Court Election

Briefing will be completed over the next 60 days with an argument likely in February or March. The timing is interesting, especially given an impending Wisconsin Supreme Court election in April 2026. Injecting illegal immigration into that race could certainly shake things up, especially with approximately 69,000 illegal immigrants in Wisconsin and splashy stories of their criminal activity.

Another wild card is the Trump administration. It has not intervened in any of the previous state cases, but could here. The case raises the issue of federal preemption, which the Wisconsin Supreme Court tacitly acknowledges with their reference to 287(g) agreements in the briefing order. Are sheriffs exercising delegated federal power? Are aliens in county jails pursuant to a detainer actually in federal custody? If either of these questions’ answers is “yes,” then this raises a preemption issue that could provide an avenue for review by the U.S. Supreme Court. An intervening Trump administration would raise the chances that the U.S. Supreme Court would step in and take the case.

But if this case just plods along as expected, then the likely result is a ruling that local officials cannot honor ICE holds, thereby obstructing ICE immigration enforcement in Wisconsin. The unintended consequences may include more ICE agents in Wisconsin, taking people off the street outside of jails and courtrooms. That’s a scene no one wants, but it may be inevitable if the court declares Wisconsin a sanctuary state.

Dan Lennington is the managing vice president and deputy counsel at the Wisconsin Institute for Law & Liberty. He is also a former federal prosecutor who enforced federal immigration laws.