lol, the self-quoting.
And yeah... the drinker has to stop himself. That's pretty much the only way. And the only way that'll happen, is if they actually want to.
My own bout with alcohol dependency was short but intense. One day, i had enough feeling terrible and decided not to drink anymore.
No one told me, no one made me, nothing prevented access... i just allowed myself to realize the association between the drink and the terrible internal distress, and knew i didn't want to do that to myself anymore, at all, ever. I had like, one, on a couple of occasions, after i made the decision. Haven't had a drop in years now. I've only had the craving a few times since, and it was easy to beat.
The drinker has to get themselves to that place first. Sometimes that's an ugly ride.
The harsh reality is that not everyone gets to make it.
Sometimes you have to watch friends/family destroyed, or destroy themselves, or even others, unduly. Sometimes you don't have to watch, but you'll still have to know.
All you can do is care and be available, and try to help if you get the opportunity to do so.