I've seen a number of people over the years who would take smoke breaks nearly every hour of the day. That doesn't necessarily impair judgment, but it may have an impact on performance. In theory this is something on which you can crackdown, but it doesn't always happen.

Actually it significantly boosts my performance, which is why I do it the first place. (Obviously if you were hiring e.g. a surgeon, whose job requires several hours entirely without interruption, that would be a different story, but few IT jobs have that requirement.)

But nobody said "enough alcohol to seriously impair your judgement," rather we were talking about any alcohol at all.

That's not what I understood. steverb said, "an employer that doesn't mind how much alcohol is in your bloodstream"