If you are the owner of a building or property in Wisconsin that allows public access, and do not wish firearms to be allowed on the premises, you must comply to Wisconsin's gun sign laws pursuant to Stat. § 943.13 (2) (bm) .
Wis. Stat. § 943.13 (2) (bm) 1. In this paragraph, "sign" means a sign that states a restriction imposed under subd. 2. that is at least 5 inches by 7 inches. 2. a. For the purposes of sub. (1m) (c) 1m., an owner of a residence that is not a single-family residence has notified an individual not to enter or remain in a part of that building, or on the grounds of that building, while carrying a firearm or with a particular type of firearm if the owner has posted a sign that is located in a prominent place near all of the entrances to the part of the building to which the restriction applies or near all probable access points to the grounds to which the restriction applies and any individual entering the building or the grounds can be reasonably expected to see the sign.