the iNat2Wiki group I am part of—a group of volunteers supporting the reuse of free-licensed iNaturalist observations in Wikipedia and sister projects and other platforms—flagged a recent flurry of deletions of otherwise legitimate photos on Wikimedia’s end that was recently caused by a bot that checks image licenses.
As it turns out, these images were originally released on iNaturalist by their creator under a free Creative Commons license (CC0, CC BY or CC BY SA) but for whatever reason their creator later decided to “update” the license to a less permissive one (for example, reverting to All rights reserved or to the default iNat license that doesn’t allow commercial reuse). See these two examples: 1 - 2
I say “update” because a free license, once chosen by a user, releases rights on the associated resources in perpetuity and cannot be revoked. In other words, if at any given time I come across a CC BY licensed image and want to reuse it with attribution on a Wikipedia page, in a syllabus, in a paper etc, I have the right to do so regardless of whether the creator decides to change the license on the same image at a later time.
We had a number of imported images deleted but were able to rescue them because the Internet Archive keeps a cached version of the original license at the time of the import.
This is a scenario that the legal team at Creative Commons can advise on. However, it would be ideal if, whenever an iNat user tries to change a free license on one or multiple images, a warning was displayed explaining that this is not possible, or at least explaining that the original license remains in effect for folks who had access to this image.