Then it is declared illegal and simply continues to exist. If this is truly a major crime (loss of life, major financial loss), then governments have many means

Then it is declared illegal and simply continues to exist. If this is truly a major crime (loss of life, major financial loss), then governments have many means outside of technology to shut stuff down: old-fashioned detective work, cross-national police work, enforcement of treaty obligations or even para-military action in severe cases. Right now, a sneeze can ban you on the cloud. And the bans are just a click away - and in many cases not even that.