Had this happen once on some property in Salem. Found a stand on the same tree we had a POSTED sign on and it was facing onto our side. They moved the sign 20ft in and hung their stand.
We left them a nice note stating if they did not move we would contact the GW. They wrote F..You on the note and tacked it to the POSTED sign. We decided to skip the GW and removed the stand, left a note on the tree with phone number, if they wanted the stand back they would have to come get it. Never heard from them again nor ran into them in that area. We tried to "run into" them several times during the season.