I think the difficulty someone might have with this sort of use of an ambulance is called - acting irresponsibly. If he was on medication that says "Don't drink alcohol" (and all anti-d's do as well as just about every psychotropic medication) then to go drinking and become a bit dodgy... is not a health emergency - "no one had even seen alcohol effect him this badly before" ... it's a lack of responsibility. If he wants to get pissed - stay home or make sure he has enough money for taxi to A&E at least... then you're only wasting A&E time instead of an Ambulance aswell.