[danarmak]

Yes, by giving the government access to one or both of the end devices. (Which is probably already a thing somewhere legally, and very likely is the factory state for some Android phones.)

Note that banning E2EE implies banning encrypted p2p communications entirely. E2EE is a concept that applies only to centralized comms providers where all messages go through a server.

Practically speaking, it's impossible to ban every encrypted protocol (TLS, SSH, ...). It's also (probably) impossible to ban IP communications that don't have an "approved server" participating.

However, comms providers / social networks to date at least manage, authenticate, and introduce users at the serverside. Fully distributed projects have problems with spam. So governments would have to ban comms providers from "allowing" their clients to talk to each other directly and not via the backend. That's a hefty technological restriction, which would block a wide range of protocols (webrtc/SIP, torrents, probably a bunch of other Very Important things I'm not thinking of right now).