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?
I think you are sincerely guessing that the man is mentally unstable because if he appears dirty with shabby looks does not really make him mentally unstable, and from your observation you did not have any proof that he is mentally unstable. and he comes to a betting shop to place his bet that means that he is of sound mind because he knows what is doing and the owner of the betting shop interacts with him as pertains their business. The only law that restricts people from gambling in any country where gambling is legalized is under age and talking about shabby or dirty looks it is left for the betting attendant or the owners of the betting shops to deal with that.
However, regarding your question, if mentally unstable people should gamble? in law of contracts they are not legally accepted to engage in any business with sane person but he or she can partake in a business when he or she is in lucid period. that is to say that the mentally unstable persons are only allowed to gamble when they are in lucid period.(when they can be able to communicate effectively without violence).