Cheryl, he already knows the answer to this. Mom's have a tendency to give sensible but unwanted advice so he's selling you a bill of goods to get you off of his back. Driving under the influence is driving under the influence, and it doesn't matter whether it's pot or alcohol. If he really believes what he's telling you to be true, then I have some waterfront property under a bridge to sell him. If he's stopped for driving eratically and refuses to take a field sobriety test and (or) breathelizer, they will arrest him for suspicion of DUI and impound the car anyway.
What's important here is not what he believes but what you believe, and especially if you're permitting him to drive the family car knowing this is going on. If he's determined to create problems for himself that's one thing, but don't let him take you down with him by permitting him to take your car. Do yourself (and your son) a hugh favor, tell him there's no approval of driving a car under the influence and it doesn't matter what it is. The results are just as disasterous either way.
What does his dad think about this?
