Legal Question in Family Law in California

Well, can he earn a living to support himself then he can petition for emancipation, otherwise is he just wanting to live with a friend's family (and presumably just do drugs and drink alcohol)?

Maybe tell him no, that he'll be a runaway as you're not giving him permission and where he will be staying will commit a crime by harboring a runaway and contributing to the delinquency of a minor. If he goes anyways you can call the police and report a juvenile runaway and give them the location. The place he is staying at will eventually not want to be in trouble for harboring a runaway juvenile. The police will go and determine whether he is a minor and the whether the place he is staying at knows he's a runaway. I believe the police will drive him back to you. If it becomes habitual the Courts may get involved, probably fine him, punish him, order drug screening, suspend his license, etc..