Also see us changing copyright law extending it years to keep Disney works like steamboat willie private in the past.

"Under this Act, works made in 1923 or afterwards that were still protected by copyright in 1998 would not enter the public domain until January 1, 2019, or later. Mickey Mouse specifically, having first appeared in 1928 in Steamboat Willie, entered the public domain in 2024[5] or afterward (depending on the date of the product). Unlike copyright extension legislation in the European Union, the Sonny Bono Act did not revive copyrights that had already expired, and therefore is not retroactive in that sense" Source: https://en.m.wikipedia.org/wiki/Copyright_Term_Extension_Act

"Sonny Bono Copyright Term Extension Act – also known as the Copyright Term Extension Act"

https://en.m.wikipedia.org/wiki/Copyright_Term_Extension_Act