Yes I agree, setting a boundary is not about control. It is not about what your A wants or needs. It is about you!
Boundaries are there in order to protect ourselves from the pain that comes from our lines getting crossed, they also help redefine what are 'lines' are. They are internal. They determine, what behaviour you find acceptable, what is not acceptable and what you will do if your boundaries are crossed.
So you don't want your A to drink in the house? I gather you want this becaue of how it makes you feel, the anxiety and insecurity that comes with it? So go ahead and have that boundary! It is helping to protect you from those horrid feelings that you know are unhealthy for you and that you do not wish to feel! If your A wishes to drink, he may go elsewhere! If he decides to cross your boundary you will need some consequences, only you can decide these. Some people here remove themselves from the house, go stay at a friends, etc etc.
The thing with this boundary (and what happened to me) is that the A may simply, not care, about your boundaries and break them all the time. For me, their was an ultimate boundary - keep crossing my boundary and I will end the relationship.
He still needs to respect you and your wishes despite his problems! That isn't control it is politeness!
Lily xxxxxxxxxxxxxxxxxxxx