Well, only you really know(really) if they legitimately belong there or not. Maybe you're not sure if they do or not. Either way it's not up to you to kick them off. If it was me, and I knew for sure that they weren't supposed to be there, my first move would be to put some no trespassing/no hunting signs on their stand trees, so they know that someone else knows they are there. That may be enough to get them out of there. I would also be trying to get in touch with the landowner, via registered mail, as of right now. The landowner may dictate your next move, giving you written permission to be a steward for their land in their absence. Even if they dont give you permission to hunt it, they may give you permission to keep others out. Problem solved, no?