I am surprised that people are using VPN while duelbits clearly states in their term of services (
https://duelbits.com/tos) that you cannot or should not access their service from a banned region. So if anyone is using VPN from a banned region, he may lose his account and funds, if got caught, so be careful.
By accessing or using duelbits.com or you confirm to be not from any banned or restricted Region. You may not access the Service from a banned Region via a VPN.
Of course it's really a dumb move if he's forcing to gamble while his country got banned.
But if it's about ISP problem and then there's no other way except using VPN. I think every successful casino should have a mirror link, this will solve ISP problem and there's no reason to use VPN except they want to hide his location which surely a red flag for casino.