Well, he is still in law school, but check this out.
A Know Your Rights Law student backs down a cop after being unlawfully stopped for carrying a gun in Portland, Maine.
Bottom line: Most cops are most concerned about their jobs. They have so many rules that they are required to follow, none of them really know when they are and are not breaking the law. If you show even a hint of superior knowledge most of them, especially in big cities, will be very careful with you. The student in this video is very knowledgeable, but you can get pretty far with a lot less knowledge, or the appearance of superior knowledge.
(ht David Kramer)