Within thirteen years of the war ending, four states legislated on their own writing. Each used a different kind of instrument, and the kind turns out to predict what survived.
Japan went first, in November 1946, with two cabinet notifications issued on the same day. One set a list of characters for official use. The other moved kana spelling off historical orthography and onto modern pronunciation. A cabinet notification is not legislation. It binds government offices and otherwise sets a standard that newspapers, publishers and schools chose to follow — and they did, comprehensively.
Korea passed a statute. One substantive sentence, in force the day it was promulgated in October 1948, on a date chosen to fall on Hangul Day. It is routinely described as banning Chinese characters. Its own text expressly permits them to be used alongside, for some time, where necessary. It defines none of those terms, sets no penalty, and names no enforcement. It is a declaration of independence written in the grammar of a law.
North Korea made the most complete change of any of them, abandoning Chinese characters entirely around March 1949. No dated instrument for it can be found — no cabinet decision, no assembly enactment, no named directive. The most thorough reform in the region is the one with no paperwork.
China used a State Council resolution, passed in January 1956, binding in printed matter from the first of February. Two hundred and thirty characters, compulsory.
A guideline, a declaration, a silence, and an order. Four ways to change how a country writes.