Are there any locations where it is illegal to openly carry a firearm or any weapon?
Yes. It is unlawful for anyone (except for law enforcement), including persons with a CCW license, to knowingly carry an unconcealed weapon (firearm, electric weapon, a knife or a billy club) in the following locations:
Any portion of a building that is a police station, sheriff‘s office, state patrol station, or the office of a Division of Criminal Investigation special agent of DOJ.
Any portion of a building that is a prison, jail, house of correction, or secured correctional facility.
The Sand Ridge Secure Treatment Center, the Wisconsin Resource Center, or any secured unit or secured portion of a mental health institution, including a facility designated as the Maximum Security Facility at the Mendota Mental Health Institute.
Any portion of a building that is a county, state, or federal courthouse.
Any portion of a building that is a municipal courtroom if court is in session.
A place beyond a security checkpoint in an airport.
Wis. Stat. § 175.60(16)(a).