The casino will list the countries that are restricted according to their licensor’s requirements. However, if gambling is prohibited in your country, it is your responsibility to verify that. It’s hard for the casino to gather a list of all countries where gambling is prohibited, so they usually add a clause like this one I quoted from BetPanda's Terms of Service:
It is up to you to ensure that you act in accordance with the laws of your home country or the country where You currently reside.
If you breach your country’s regulations, you may face more severe consequences than just having your account banned.
It's written in ToS and it's responsibility of users on what they do.
Practically, gambling is prohibited in many countries, Bitcoin and cryptocurrencies related activities are illegal or allegal in many nations, but people still do gambling or activities with Bitcoin and cryptocurrencies. When doing this, they are aware of illegal activities and must be affordable with any legal issue in future.
Reading that is the first thing needed to do but people are so lazy locating it because what they usually like is to gamble immediately.
They got only surprised once being detected and throw bad shade on the casino for experiencing troubles regarding on the violations they encounter. That's why to avoid this consequences they better read the TOS since this is important action to do so they would know if they are allowed to gamble also what are the other rules implemented including those prohibited actions to be done so that they can avoid getting issues and gamble without anything to worry.