The latest installment in the "Government doesn't understand math" series
When encryption and secure messaging is outlawed, only outlaws will have and use it.
Freedom is won in the courts and the legislature, not in the code (although tech is as useful tool for keeping government implantations in check).
(I still use and donate to Signal, but have a healthy understanding of its limits)
Freedom is won through weapons. Encryption is a potent weapon, it can defeat states, militaries. Before computers, it used to be a military tool. It must be democratized, the whole world must use it.
They don't necessarily need to outlaw it. They may just throw up enough hurdles that it doesn't become a major success. Developing a communication system that is secure, featureful and convenient to use for the general population is not a trivial task. A large effort that can be undermined.
E.g. if they only require logging from communication service providers but not from application developers then this would force a decentralized solution. If they lean on payment providers it might get difficult to charge for phone apps or get donations.
The software could continue to legally exist but see little adoption. Which is enough to enable surveillance.