"I quoted the law - to 'prove' he was legally in this country, all he had to show was a driver's license"
You are confused by written language. You should read it carefully.
It says you may need to prove citizenship if you get stopped for a traffic violation. That driver's license must be " issued by an entity that requires proof of lawful presence in the United States before issuance." In a few words my NY license wouldn't qualify.
You should not be obliged to prove you are a citizen speeder. Pretty soon someone will come up with the idea that they should also check you for venereal disease, and downwards from there.
It's a stupid fascist law in a free land. I will NEVER carry ID with me, anywhere, unless I am driving at which point I'll have my driver's license and that's it.
It's a slippery slope they're taking their people down on, down there.
They should start enforcing labor laws, and require citizenship for work, and punish those who hire illegals rather than piss off the rest of us with garbage like that.