That's sad and wrong.
Yes, he can drink as much as he wants. Yet mentally losing it should allow for some kind of medical intervention at some point.
I'm sorry you're dealing with this and not getting much needed help.
My husband stayed in a mental health program for a week and was drinking fairly soon after discharging, yet it was one of the touch points for family members having time to connect with him in a positive way and my experience before he was admitted was that he was a danger to himself and others. He was not living with me at the time and I didn't show up in person until the family day, yet I was able to work with facilitators by phone to help encourage further treatment instead of releasing after 12 hours of hospitalization.