I've seen and heard many a story on checkpoints. In PA they will stop everybody, not just hunters. They will ask questions and ask to open your trunk. If you refuse they tell you to pull over on the side and they will get back to you later. It could be hours! The assumption, they tell you is because you refused they have probable cause and will get a warrant and they don't do that until after their done with the checkpoint. If you just leave they will stop you and now you're obstructing so they search your vehicle. There have been many arguments and precedents as far as checkpoints (hunting and none) and the fourth amendment. You would probably win in court , maybe not but are you going to spend hours and hours and days fighting it? That's what they bank on.