I say he wants to be a grownup, break the law like a grownup, then he has to face the concequences of breaking the law as a grownup. Which means, let things fall as they may. He needs to learn the real concequences of breaking the law.
On the homefront, if he has fines, he needs to get a job to pay for said fines. or, if they have to be paid immideiately you pay them, and then he gets a job to pay YOU back for the fines.
Parental imposed concequenses will really mean nothing.
YOU dont react. Let the law handle it, he broke the law, he needs to deal with it.
Too many parents bail their kids out of trouble with the law in hopes they'll learn a lesson. That's not how they learn. The natural concequence for breaking the law is dealing with the law's concequences...
Have him clean around the house/yard to earn the money for fines.
I would have a list of things for him to do after school everyday and he couldn't see his gf or use the phone/computer until the things on the list were done.