Out of state students are not required to have a DL for that state. Europeans and Canadians do drive our streets without that state's DL. But, I do not know if a European can drive our streets for a year under a work visa. If a student can legally do it then I'd imagine a worker can do it too. I have four nephews that attend school in LA, UT and WA for four long years. None of them got DL's from those states.
As for a cop only needing PC, maybe? But he is supposed to be trained in what is legal and not legal...and not just write people up on a hunch as you infer.