if they have a drivers license then immigration can link databases check if their in the country legally and deport them.
if I were illegal, I would not want my name in any database. You think the cop is going to take an illegal with a drivers license and not check if their visa or immigration papers are valid or refer their ticket and drivers license number to immigration.
I was against it...but I can see that the next logical step is to link the immigration database and the dmv database so the cops can check both during a pullover.
You could get arrested for an expired license and over-staying your VISA for a simple traffic stop.