do this - take the stand and steps down, and leave a nice note on the tree (tied to the tree, in a ziplock bag) to come to your house, or call you to recover them and you'll be glad to do so. Or, give them to a Game Warden and have the guy contact the GM to get them back.

DO NOT do anything that would risk the guy getting hurt - thats a liability to you. Be nice about it all, thats the way to be.

What MIGHT happen in the future you don't know, you can only take certain measures and go from there.

Contact a GM, explain it to him, maybe he'll come out and witness the stand and the removal ? Video tape it even. Get the evidence, leave the note. Its about all you can do other than a stake out