A) They are Federal Law Enforcement Officers. That should be your first clue.
B) They are Federal Law Enforcement Officers.

Did I make that clear enough? I have a good friend who used to be an FWC officer. (Now a US Customs Officer) He pulled people over all the time for speeding. He'd be cruising at 70ish mph, and people would pass him like he was standing still. He'd pull them over and their excuse was the same all the time "I didn't know you guys could issue speeding tickets".

The DOT guys can do it as well. Just don't be fucking retarded around law enforcement and you won't really have a problem.