I was queueing up in the supermarket earlier today when two young girls (say, 16/17 yo?) asked me if I would buy a bottle of red wine for them - apparently it was to be a present for someone.
I've no doubt it was - who likes red wine at 17 yo? 
I told them 'no, I'd be breaking the law, go away and get older!' they got rather huffy and stalked off, and I mentioned it to the checkout lady.
As I say, I'm pretty sure they weren't buying it for themselves, but all the same, I didn't particularly want to break the law, and I'm sure the checkout lady would've been in trouble too!
Was I being 'the fun police' or did I do the right thing?