The first problem here is we are talking about public land, so other than calling him out on it, there is not much you can do. But, a few things you can do. 1. Start deleting/changing waypoints in his GPS. 2. Air out his tires next time you find him on your honey hole without you (just let the air out, don't slice his tires). 3. Start talking up some random piece of public hunting ground, the more hunters and less deer there the better.

Good luck dealing with this guy, I am sure you can thing of some more very fun ways to mess with his honey hole stealing ass.