It's too late for that, every machine, every browser, every user is using encryption software all the time.
"It's too late to criminalize possession of drugs. Half the country takes pharmaceuticals!"
It's trivial when you can pass arbitrary legislation.
Back in the 90s we had to deal with US gov restrictions on encryption export. Software companies and organisations fell into line. It was a big deal when 128-bit keyed Netscape became available globally in 1997, per State Dept approval, but even then the full-strength server-side SSL was still restricted to 'approved' entities.
And even 56-bit server SSL was only exportable with us.gov key escrow.
I used to use Apache with the 40-bit SSL option. Pathetic strength but no-one was going to risk jail-time by breaking laws.
I did at that time, it was just another law to ignore.
This isn't meatspace, the dynamics are quite different.
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).