If his insurance and driving license were all up to date, and no outstanding warrants, probation and all that then it is likely he would be let go or at the very least the car would be towed/impounded and released.

I believe this can sometimes happen based on my experience as a college kid when my father was pulled over for really excessive speed in his Acura on 84 in Manchester in the HOV lane, well in excess of a misdemeanor level @ 120mph or so. It was fun as hell trip home from college until we got pulled over. As soon as Dad saw the cop he slowed down and pulled over. The cop was spitting mad but let us go on a promise to appear in court. Eventually in court with a traffic lawyer it got brought down to a points level speeding ticket w/o reckless driving or any other charges. Of course we weren't DWB, so things may differ based on your skin color.