This afternoon, at a supermarket checkout, I witnessed one of life's absurdities. Two people, together but paying for their shopping separately, were both buying alcohol, along with food. They both looked as though they were about 20. The gentleman was asked for proof of age, and produced it, so he was allowed to buy his alcohol. The lady was asked for proof of age, but had none, so she was not allowed to buy hers. Could the gentleman buy her alcohol instead? No, because he would be buying it for her, and that would be illegal if she were under 18. We were all held up while a supervisor was summoned. She confirmed the ruling, and the supermarket lost a sale of three bottles of bubbly.
If the gentleman had gone round the shop again, picked up identical bottles, and presented himself at a different checkout, he would have been able to buy them. Moreover, the lady might not have wanted the bottles for herself. They might have been to give as presents. In that case, the gentleman could have bought them, and given them as presents himself, all within the law. And it is entirely possible that once the couple got home, he would have opened a bottle from those he did buy and shared it with her. The law against buying alcohol for someone else, aged under 18, to consume off the premises of purchase is unenforceable.
I assume that the supermarket acted from an abundance of caution. The couple might have been agents provocateurs, checking on behalf of the police that the law was being enforced. If they had been, and if the supermarket had nodded the purchase through on grounds of common sense, the police might not have been sympathetic.
This raises a question. Is it possible to build common sense into rules? Suppose that an exception for this kind of situation had been written into the rules. The exception might be for situations where there was one person in a group who could prove that he was over 18, offering to step in and purchase alcohol that had been in the shopping basket of someone else who looked as though she was probably over 18, but who could not prove her age. That would not help when the second person looked as though she was under 18, but was in fact over 18, and the first person offered to be the purchaser in her stead. (Then the first person would just go round the shop again.) A comprehensive set of exceptions, that would have the same reach as common sense, would be impossible to compile. This does not make defined exceptions useless. They can eliminate many absurdities. But they are not likely to be a perfect solution.
I suspect that the main problem is that enforcers expect 100 per cent compliance. If they were prepared to ignore a small rate of rule-breaking, especially when the offence would be victimless (buying alcohol for someone who, if under 18, was not much under, or smoking in an enclosed public space), life would be better. Enforcers could tighten up if the rate of rule-breaking started to rise. We should not assume that all slopes would be slippery.