If encryption is banned, the Internet collapses. You're not accessing Facebook because Facebook can't fund itself anymore (the companies who used to pay to get Facebook to target their ads towards them are no longer doing it because they can just wiretap all the information they want from users and place their own targeted ads).
Every time you access the Internet now, you're given the site you want after 20 refreshes (sometimes), before then you're either getting a time out error (likely due to ddos and bad packet management because servers can't use keys to regulate that/verify users a real) or you're getting an ad to somewhere else or just a blank page because someone somewhere wants to see if they can do it (anyone can pretend to be a dns server if they want and point you wherever they like now SSL is no longer a thing).
FBI, CIA, NSA, MI6, FSB and all others alike would collapse.
All military system would be reduced to sticks, screams, rocks, etc. No communications, etc.
I mean, I can't see this even a possibililty. Nowadays, information, data and privacy means much more than what we think. I know that common and mortal people are already being harassed with privacy violations and etc, but imagine governments, states, counties, military, agencies, etc, without any kind of privacy... I can't picture that!