Wis. Stat. § 192.47
Any railway company may, at its own expense, appoint and employ railroad police officers at the stations or other places on the line of its road within this state as it deems necessary for the protection of its property and the preservation of order on its premises and in and about its cars, depots, depot grounds, yards, buildings or other structures. Each police officer shall take an oath to support the constitution of the United States and claiming to be a citizen of the United States and shall file it with the office. Each police officer shall, when on duty, wear a shield furnished by the company bearing the words "Railroad Police" and the name of the company. These police officers may arrest, with or without warrant, any person who in their presence commits upon the premises of the company or in or about its cars, depots, depot grounds, yards, buildings or other structures any offense against the laws of this state or the ordinances of any town, city or village, and shall also have the authority of sheriffs in regard to the arrest or apprehension of these offenders in or about the premises or appurtenances. In case of the arrest, by a railroad police officer, of any person without warrant the officer shall immediately take the offender before a judge having jurisdiction and make complaint against the offender. Every railway company shall be responsible for the acts of its police officers.
Wis. Stat. § 192.47