If anyone ever shows up at your door to tell you one your son was killed by a drunk driver and you found out someone could have intervened and didn't, what would you do and how would you feel? I think the answer to your question is this, by letting him drive off drunk, you would have to accept that your child died when they didn't have to. Everytime they drive off drunk and you do nothing, you made the choice to protect the drunk driver and not the innocent people he may plow into. By not calling the police, that isn't really protecting him either. What if you let him drive off and then get the call he just plowed into a tree or someones house? The right and responsible thing to do is not the easy thing to do.