Fedora to disallow CC0-licensed code

CC0 code is not subject to copyright protection. There is nothing (besides common decency) stopping me from taking some CC0 code, changing it just enough for copyright to attach (e.g. minor stylistic refactoring, mass variable renaming, etc.), and then slapping my own copyright notice and license on it, and completely removing the CC0 notice altogether. The law (at least in most jurisdictions) doesn't consider that to be infringing, because the previous author has waived all of their exclusive rights in the existing code (although, in some jurisdictions, there might be issues relating to moral rights). Seeing as Fedora can't reasonably be expected to know the full provenance and history of every line of code they distribute, I don't see how they can prevent people from doing something like that.

(Of course, Fedora also can't necessarily stop people from outright *lying* about the copyright license, but at least in that case they respond when someone sends them a DMCA notice or cease & desist letter. With CC0, there's no underlying infringement, so nobody is ever going to tell them!)