And what responsibility does the impaired person have? Are they not to be held accountable for getting impaired? If my husband blows the mortgage payment on poker losses, I'm certainly not going to blame the guys he was playing poker with, or the fact that he was "impaired."
It seems that both of them should be held accountable. The drunk for getting drunk and the proprietor for getting him drunk AND facilitating a risky behavior (gambling). That is why you need a "cooling off" period or removing the liquor from the equation to reduce the risk.
We have a cooling off period for products. Why not gambling?