Are you talking to a land base casino? if yes I would say no, they are not criminals since the casino needs permission from a goverment to run in a city and they not conmen too because players will not enter and gamble in their casino if it is true.
No, it's not like that! There are mobsters and gangsters who have ties with gambling industry. FBI even hunts them down. I am not saying that all the casinos are run by criminals but you can Google and find out about such casinos in Las Vegas. Also, my friend it is too naive to think that government has no links with underworld or criminals and they are two sides of the same coin...