This letter is simple trespass notice. Did you get your notice, mooted by ss 943.13(1m)(b)
1m) Whoever does any of the following is subject to a Class B forfeiture: (b) Enters or remains on any land of another after having been notified by the owner or occupant not to enter or remain on the premises. This paragraph does not apply to a licensee ...if the owner’s or occupant’s intent is to prevent the licensee ... from carrying a firearm on the owner’s or occupant’s land.
It must be posted! ss 943.13(1s) and ss 943.13(2)