The same way you can't send money to the best Korea and watch porn on youtube.
There is a long chain of actions that ends with you having e2e on your phone (or what not). At the starts of it there is your physical body living in jurisdiction and transacting with (mostly) other people being somewhat present in the same jurisdiction using government-captured money. There are multiply choke points, controlling which will not result in 100% enforcement, but will make whatever you want to do a huge pain in the ass, so most people will not bother (case in point -- jailbraking). Whoever is left self-selects themselves for selective enforcement.
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I am not sure I follow. I can't watch porn on YT because YT decides not to host it. But I can absolutely use a VPN and access porn in a jurisdiction that does not block it. I can also, and in fact do, encrypt my hard drives. Even China can't reliably prevent communication over private encrypted networks or services hosted overseas.