Some countries consider online gambling as illegal activity.
So yes, it is in those regards. But that is the beauty of being online. You can use a vpn to not be in those countries while doing those activities, so it is like you are not even in those countries that ban it.
Yes. On my country, Online Gambling is illegal.. But i think most illegal of bitcoin at here is anonymous coins. So buy smt like that : gun, drugs,...

=> Illegal more at my country! But our goverment don't ban it, they only notice us about BTC!