He shouldn't have pled guilty. He should have used his right to remain silent, and called a crim law attorney as soon as he was released from custody.
If he pled guilty, he's very likely screwed on legal procedural ground. He can look at expunging his record (depending on state/jurisdiction) at some point and I highly recommend he do so, even if this is a misdemeanor. If it was a civil infraction, then there is no criminal record.
That is what I told him. Just wondering if he can change his plea or appeal?