In the UK, self-service checkouts can sell alcohol, but the transaction must be approved by a human - at least, in all the supermarkets I've seen.
Is it possible to do this without human approval and still be legal?
I'm a personal license holder, so I've some familiarity with the law. Each sale must be authorised by the license holder - but this authority can be delegated. Also, whoever is making the sale must check the person is of age, not drunk, and there's a couple of other subtleties. What I don't know is how exactly this could be interpreted.
A self-service checkout can do an ID check - perhaps you need manual verification for your first purchase, and using the same credit card in future allows automatic approval. Checking for drunk customers is harder, but perhaps the store could have a blanket "no drunks in store" policy.
Is there any history of any store trying this? Is it legally a non-starter?