If you have ever watched on of those YouTube videos where someone is held at an internal traffic checkpoint and passively resists the officer's demand to pull over and consent to a search, then this article is a must read.
You have certain constitutional rights, and the police are going to attempt to push you away from them as hard as they think they can get away with. It's amazing how many people simply agree to allow a detention and search of their car without probable cause, in order to avoid conflict with the men in uniform. Know your rights!
Here is a good example of what happens when officers at an internal checkpoint are challenged on their constitutional right to stop, search and question. Caution: doing this with a bad attitude to the wrong cop is going to get you face down in the dirt with your hands cuffed behind your back. If you are going to assert your rights, know what they are, be super polite, and explain what you are doing, so the cops get it, and don't decide you are a crook.