Put a big NO TRESPASSING sign right on his stand. Someone did it to me whenI unintentionally set a stand on private land. It works!!! Just be polite. You don't know for sure who it is. It could just be a misunderstanding. I'm guessing it's not though. I would say to warn the guy and if he doesn't get off take his stand. It's legally yours.

Give the man warning though. I had a misunderstanding with land boundaries and ended up getting people ticked off at me.I had one stand stolen and got a guy pissed off at me. It was all one big mess of different people thinking different ways. My uncle told meI could hunt anywhere because that was the agreement and it turned out to be the wrong move. I'm just telling you that not everyone has ill intentions. Be polite to him until he won't bereasonable.