I think it can be done, as long as they don't change it right away. They can give a certain amount of time after they take the rule.
I think recently there have been many casinos that have implemented it, for example I mentioned stake which changed their rules at the beginning of this year by requiring it, after previously without KYC users could still make deposits, play and withdraw. However, they also don't just implement it, but they routinely provide information about KYC every day.
Yes, in fact there is something that can be implemented in casinos without causing so much fuss, since everyone now Demands and it is mandatory to have KYC, because every time you are going to make a large Withdrawal, instead of Postponing it and making you have a bad time playing, what you should do is a small KYC as is done in some exchanges, including Binance , and that will not take more than 5 minutes to do and once that is verified then you can withdraw , which is what causes the most problems.