CC0 is explicitly designed with such legal issues in mind and includes a license for legislations that do not have direct way of putting works to PD

> If the waiver isn’t effective for any reason, then CC0 acts as a license from the affirmer granting the public an unconditional, irrevocable, non exclusive, royalty free license to use the work for any purpose.

https://wiki.creativecommons.org/wiki/CC0_FAQ#How_does_it_wo...

https://creativecommons.org/share-your-work/public-domain/cc...

Alright thanks for pointing that out, I misremembered it then.

The point of CC0 is that it puts things in the public domain if possible, and provides the most liberal license if not. See the "public license fallback" - https://creativecommons.org/publicdomain/zero/1.0/legalcode