I understand you're concerned - but.
Maybe I'm the only person who will say this - but.
He's just gotten home from rehab. He's transitioning and he's probably going through alot.
He is still sober - yes?
Maybe give him some kindness and compassion and see how things play out over the next couple of weeks.
He's likely overwhelmed and trying to find his "sober feet" at this time.
Reality is - if he's gonna drink - there's nothing you can do to possibly stop it. Bombarding him with concern or trying to put safeguards into place will likely only make him rebel - and give him a reason to blame you for his relapse.
Work on you - give him some distance. He's attended 4 meetings and that's excellent.
Did you expect him to come out perfect?