My company recently disabled the 21+ bypass button for liquor and we have to scan all id's regardless of age. No valid id for liquor no sale. Even if you're 95+ and don't have a valid one.  Goodness people sure can get pissy about it. And yes if a customer is an @$$ hole about refusing to present id we have to deny the sale. You could be 75+ and throw a tantrum over it and we can refuse the sale.