Some countries block exchanges within their jurisdiction from offering Monero, for example, but it can still get obtained via other means. Peer to peer, offshore exchanges, decentralised exchanges.
Not sure if you meant "in general". Whatever the government decides is a crime, is a crime.
Slavery is banned. You can't own people. For some crimes countries like having extraterritorial jurisdiction, too. E.g. FGM "tourism" and child sexual exploitation. It's not just warcrimes that are extraterritorial.
I'm not equating these, certainly not morally. I'm saying that saying "outside the control of government" and "can't be banned" is either false, or applies to any other crime too.
And if it applies to all laws, then that's basically the sovereign citizen theory of laws; people getting the legal consequences for their actions all while saying "you can't do this", where "they" demonstrably can.
