Earlier quoted context omitted.
Laws are an issue and enforceability is an issue. If a largish group of users could create end-to-end encryption not with a single company but with "readily available materials", then stopping it could be harder. So it's a combination of state dictate and the practical ability of users to defy that. This isn't saying I'm optimistic, I'm rather pessimistic on any ability of a wide home-grown encrypted-messaging milieu…
Possession of encryption software could be treated the same as possession of drugs. On the next stop and search you would only had to handover your phone. If police password will not work it will be confiscated. If encryption software is found you go in the dock. It is the future. Society accepted ridiculous laws to jail people for having a plant, they'll accept jailing for programs. Only terrorists, thieves and adul…
Well, then clearly it would quickly become ubiquitous. I mean, if a war on encryption that was just like the war on drugs were to be launched, why my local stream bed might "place burned passwords here" on the tin-can that currently reads "used needles here." (put there by the other homeless people).