One for the road?

A Scotland Yard Commander with special responsibility for alcohol abuse has suggested that it should be an offence to buy a drink for someone who is already drunk.  Interesting idea, and made with the best of intentions, but completely impractical.  For starters, it takes no account of the fact that drunkenness is a cumulative process - you may be OK when  I buy you a drink, but that drink may be the one that tips you over the edge into drunkenness.  Have I committed an offence or not? Then - define drunk.  This is obviously aimed at the rowdy, fighting drunks, but not everybody is like that - for plenty of people alcohol makes them mellow and friendly - are they to be treated the same as the yobbos?  Like I say - impractical.