A question to all those who are staunchly defending the supermarket: do you actually think it's a GOOD rule/policy? I mean, does acting as if anyone accompanied by someone who might conceivably be under 25 is about to supply alcohol to an under-18 actually achieve anything in the great war against alcohol abuse? Really?
No. Of course not. The ONLY effect of this rule (I hesitate to call it a law, because it seems to me that bolograph knows a lot more about the actual law than most people on here) is to annoy people and possibly force them to shop elsewhere.
The fact that there is so much confusion, and people are routinely purchasing alcohol accompanied by teens and not being challenged suggests one of two things: either, it's NOT a real law, but just some sort of trumped up supermarket policy; or it's not being policed properly and, if and when it does become properly enforced, there will be no confusion. In that scenario, the questionable teen will know never to accompany the purchaser to the checkout and will stay well out of the way. Net result: no challenge at checkout, alcohol delivered smoothly to underage drinker.
This is a rule without sense. It is just an attempt to tick a box.
Finally, to those who keep reiterating that the cashier might lose their job. I'd be very sorry if that happened, but, with the greatest respect - why is that my problem? Bolograph has pointed out how the law actually works. If an individual supermarket decides to implement a sledgehammer-type policy that punishes employees with the sack unless they behave in a frankly unreasonable manner at the checkout, then I'd file that issue in the column entitled 'The Supermarket's Problem' and well away from the column entitled 'My Problem'. If the supermarket loses business due to this heavy-handed policy, I would file that under 'Poetic Justice.'