Typically, possession of marijuana without a license or doctor authorization is a criminal offense in most states. Depending on the amount of marijuana, the prosecutors can charge your son with possession with an intent to distribute (sell) marijuana as well, which is a felony in most states. I would first speak with a criminal defense attorney for your son due to the current charges he faces as well as a potential probation violation due to the new charges. Recreational use is still criminal if the person is not authorized to possess the marijuana.