In most US states, if you "brandish a weapon" on a person not making a threat to you, you'll not only be going to jail but you could be on the losing end of a multi-million dollar lawsuit. Finding someone camping on your property is NOT a legal reason to point a gun at them - you can call the police and have them deal with the person and possibly arrest them, but anyone who says they have a right to point a loaded weapon at a camper is going to not be a property owner much longer if the camper takes 'em to court.

Also - if the camper tries to leave and you prevent the person from leaving, you're looking at kidnapping and unlawful detainment charges, possibly felonies.

You certainly have the right to kick people off your property and prevent them from coming in, but if you take matters into your own hands as the testosterone-filled guy with the gun stated earlier, you're going to jail and probably getting sued.