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You'll find that many municipalities in Wisconsin have old ordinances on the books regarding the bearing of firearms. Back in 1995 these ordinances were invalidated when 66.0409 of the statutes went into effect. In a nutshell, this statute prohibits any municipality from enforcing any local ordinance that is stricter than state law regarding the ownership, possession or bearing of firearms or ammo.
State law regulates concealed carry, firearms in places that serve alcohol, in public buildings etc. So a local ordinance can regulate similarly, but since there is not state law that prohibits firearms simply "on public property" so local ordinances which do that are unenforceable.
Interestingly, some years ago, I found one municipality, Alma, which passed a firearms ordinance AFTER the preemption statute was in effect. I wrote to the city (village?) of Alma and they eventually just sent me a BS response from the city attorney-- but that's another story. The problem is that many municipalities either do not realize that their ordinances may have been invalidated, or, they like to pretend that they haven't been.