Re:GITenberg is an open source community for publishing eboo...
by maxerickson on Sunday August 02, 2020 @09:47PM
(#24033418)
CC0 isn't an indemnity.
The difference between falsely claiming something is public domain and falsely claiming to grant a license to it under CC0 is going to be pretty minimal (and is likely result in little more than "please stop", blood and turnips and so on).
Public domain obviously can be ascertained, but if CC0 hasn’t been granted we rely on dated reproductions: basically a photograph of the artwork in question in a book or journal with a copyright date of 1924 or earlier.
(that’s obviously specifically a US legal reading, but SE from a legal point of view is a US project)