As far as I know gambling is regulated and is allowed in nations that does not ban gambling so I think it is wrong to assume that gambling in general is ban or not allowed in all country.
Typically, A country that is restricted on a casino can’t access the casino website by using the regular IP for that specific country so there’s no need to check for the casino ToS if your country is not allowed unless you are always using VPN on your browsing that makes you dodge the casino restrictions unnoticed.
True, there is a notice that the country is restricted when accessing from the restricted country. Or sometimes, the country ISP block the website like in my case, some casino platform is blocked by my ISP and I cannot access their site. I am lucky that Duelbits is not among those casino sites that were blocked by my ISP.
And yet these player that were caught act like innocent saying that they don't know even some deny their action of circumventing the restriction of a casino.