I have made some findings about this before if I remember correctly. There are people that have sued gambling sites before but the result has always been the gambling site winning the lawsuit. So just know that if anyone sue any reputed gambling site, the gambling site may win the case.
I think it depends on what the case is that will determine if the gambling site will win. If a gambling site goes against breaching of contract whereby they have refused to pay a gambler money that was won, I don't think this will be a case that a gambling site can escape from because action like this, it means such gambling site can't be trusted and it is not safe for gamblers to have anything to do with a gambling site like this.