Licensing of Operators
There is no sanely manageable way to have encryption with a magic back door.
So this is all headed ultimately in the direction of licensing, just like telcos are licensed. You want to offer a service and collect revenue? Gonna have to respond to warrants or have your revenue streams cut off at source and your domains blocked.
The Chinese have their great firewall. Everyone else is headed that way too eventually so that they can wield that kind of stick.