I agree that the consequences of the mistake should be the user's responsibility. He should read the casino's terms and conditions. If the casino doesn't serve him and he uses a VPN, for example, he assumes he knows and continues anyway, so the mistake is entirely his, so the consequences should also be his.
While that is true, how many of us really read all the terms and conditions in detail? I never do it but whenever I have a question, I would go into livechat to get an answer (or ask on this forum) to make sure I am not breaking any rules that could have a negative effect on my account.