If you're interested in this subject, track down a copy of Edward Zuckerman's 1984 book
The Day After World War III (
https://www.goodreads.com/book/show/1415128.The_Day_After_Wo...). It's now sadly out of print, but it's a treasure trove of great contemporary reporting on the U.S. government's Cold War "continuity of government" plans. ("Continuity of government" being the delicate bureaucratic euphemism for how they intended to keep society from collapsing if the bombs should fall.)
It was a mention of a secret, apocalypse-only regulatory code in Zuckerman's book that got me on the trail of the Code of Emergency Federal Regulations (CEFR), which I worked with the National Archives to make available to the public back in 2016: https://jasonlefkowitz.net/2016/10/presenting-a-bit-of-histo...