Recently I was around a physical bet shop close to my area and I observed a man who was shabbily dressed walking in the gambling house. I got into the place to observe what his intentions were. He walked straight to the gaming attendant, placed his bets in a highly coordinated manner and quietly walked out of the physical gambling house. From the way he was well organized, you will never know that he was mentally unsound apart from his dirty clothes and unkept hair and beard.
When I inquired from the attendant, she said he was a regular customer and that he usually raised money for gambling through the manual jobs he does around the area. She also told me that he has never misbehaved and acted violently in the gambling house so she was comfortable with him.
My question now is are there any moral, ethical or legal obligation to bar a person from gambling after physically observing that he is mentally unstable?
In my opinion there is no problem with that, as long as he can still follow the rules in the gambling house.
Maybe mental disorders only occur when he is at home, and we don't know what factors influence it. But when he entered the gambling table, he was like a normal person without anything silly he did.
Moreover, there is no specific prohibition on people being prohibited from entering a gambling house with a shabby appearance, the important thing is that they bring money to enter there.