There was a SCOTUS case last year (?) where a murderer was attempting to overturn his conviction on the basis of an Iowa law that prohibited any part of the license plate, including the county in which it was issued, from being obscured. He was trying, unsuccessfully, to say that the county name being obscured by a frame didn't make it 'obscured.'
The State had argued, ultimately successfully, that the deputy was well within his rights to stop the murderer's car, giving the justification that if they see a car in their area in the middle of the night from some other perhaps far-away county, it gives them sufficient pause to have the right to investigate it.
I don't agree with the decision, freedom of assembly and right to travel unmolested and all that, but nevertheless, the guy's conviction was upheld.
He’s full of crap about the obscuring issue, but I agree that being from a remote county is neither probable cause nor RAS.