Stopping son from dangerous drinking

Having an errant teenage can be a scary time. It sounds like you've already done all you can do. And you picked up your lecture may have limited meaningfulness. Outstanding observation! As a parent of a teen, you no longer have control of him. You can influence his choices and role model adult behavior. You can give reasonable consequences for the drinking and you can educate him about your concern by showing him the consequences of drinking in the family. You can't turn back the clock and lock him up or supervise him with his friends. Tell him you expect him to respect your wishes. He will make the choice whether to listen or not. At 15 years old, all you can do is send strong and clear messages. You don't want to damage your credibility by over-stating your case and risk alienating him from talking to you or worse yet give him a thrill every time he defies you. Severe punishment and/or convincing him of your fear of his future risks distorting his self-concept into believing he will be a drunk too.  Your exercise of good judgment when giving him the message provides him with a model of good judgment he may choose to integrate at some time in the future. Demonstrate that you believe in his ultimate good choices, if not now, in the future. Then he will see the opportunity for change if and when he needs it.