@croydon - I don't know, I think that generally the way laws work at the moment aren't too bad. It's usually young people who are dumb enough to be lounging around in public, drinking, and you don't want the penalties for them be too bad before they learn sense, or they could end up in jail for nothing more than having a beer in a place they shouldn't.
That's the current consequences for kids who make the mistake of having a joint with some friends (or at least, the mistake of getting caught for it) and it can ruin their whole lives.
I agree that there is a problem in some places but I don't think penalties are the answer. I think providing alternative venues and activities is a better idea. Often the kids are drinking because they really don't have anything better to do.