This is a very tough position to be in, especially for a young man just starting to learn how to be independent and a responsible member of the adult world.
You need to check with the driving authorities about the requirements for getting his license back. In many parts of the US, if a person with a seizure disorder has been seizure-free on medications for 6 months, they can regain their right to drive.
This typically requires getting a form from the driving authorities to bring to his doctor. Once the doctor "clears" him, he can begin to drive again.
Please let me know if you have any follow up questions about this.
Drinking alcohol is never a good idea in the presence of a seizure disorder. The alcohol lowers the seizure threshold. Withdrawing from alcohol can also precipitate a seizure.
That said, some individuals find that they can have a drink or two without adverse consequences. He should work with his doctor or neurologist on determining what a safe level is for him.
Another option would be to encourage him to drink non-alcoholic alternatives when he goes out socially. At 17, he needs to learn how to take care of himself and act like an adult, and this often involves discipline and self-sacrifice. If he had a seizure while out with his friends, he would likely be very embarrassed and might become an imposition on them.