Sorry but it is not your land so you don't get to decide who or where people hunt. One sure way to get kicked off of a hunting spot is to act like you own it.

One thing I learned from an old hunter once, is don't go kicking other hunters off or intentionally messing with thier hunts if you are planning on hunting other peoples land.

Bottom line is, if your father-in-law wants him there he will stay there. You don't have any more right to the area than he does. There is no first come first serve. This is not Burger King. You can't always have it your way.

Is this ethical, fair, that is not your call on someone elses land.

If you park on the street do you claim the parking spot in front and behind you too, just because you were there first?