To turn "If you've been drinking, stay away from us" into a boundary you need to turn the focus off of him and back onto yourself, so it would become something like "I will not be around someone who is drunk". But what that also does it put the onus for action on you, since you can't change what he choses to do. In your case it sounds like its going to be a tough boundary to maintain if he keeps showing up wherever you've removed yourself to, I'm sorry about that. My A does that too and I have still not worked out what to do about it, short of a restraining order, eight years on!