What law determines when you have been ordered to pull over for a traffic stop?

Question

What laws in the U.S. (specifically, Massachusetts) govern *when* you need to pull over for a traffic stop? I understand that if a police vehicle comes up behind you with lights flashing it's clear that you have to pull over and stop.But what if a uniformed police officer is standing on the side of the road waving for you to pull over?What about a uniformed officer police just looking at you? Obviously evading or disobeying a police officer when he orders you to pull over is illegal. I'm wondering what constitutes a such an order.

Answer 1

Police cannot legally randomly pull you over for a traffic stop. "Probable cause" is required meaning "reasonable cause" which typically involves a safety issue for others on the road if not yourself, e.g. drunk driving, speeding, brake lights not working (fix-it tickets), expired registration, etc. Once they pull you over though, the Supreme Court has widen the latitude for a legal search in that they can now even look in your glove compartment and your trunk theoretically for open containers, weapons, and illegal drugs. Yes, it is illegal to disobey an officer even if you think they are violating your constitutional rights, but best argue that with an attorney after the fact than argue with the police at the time. As for the hypothetical about a uniformed police officer waving you down at the side of the road, I doubt that would ever happen in the first place. Lastly, we all have the right to simply look at people, and so do police officers.