The federal courthouse for the Western District of Wisconsin in Madison. John K. Wilson/WPR A lawsuit challenging the authority of county sheriffs to work with federal immigration authorities is headed back to state court. The case was filed last year by the ACLU of Wisconsin on behalf of the immigrants’ rights group Voces de la Frontera. It challenges what are known as immigration detainers, where U.S. Immigration and Customs Enforcement, or ICE, asks local jails to hold someone for up to 48 hours.