What happens when someone changes their license on an image (or other file) and you are actively using it on your website?

Question

Say I find a CC0 (public domain) or other Creative Commons Share Alike (permissive license) image on Flickr or the web. Or any asset/file really, that is under a permissive "you can use this royalty-free/copyright-free/etc. for commercial purposes/etc." license. Say I use that image on my website, or that audio file, or video, or document. All is fine and well because the license was permissive.

But then say the original content creator changes their license to be more restrictive, that is, you can't use it for commercial purposes, or other restrictive limitations are placed on the image/file. But I am already using it, given the old license. What am I to do now?

1. There's not really an easy way to be notified of file permission changes on the web. You'd have to wait for the author to manually tell you they did that.
2. Even if they did tell you they changed it, what is to be made of the fact that you used it when it had a permissive license?

One example of this is on Flickr. I am not sure everyone is aware of how licensing works who uploads photos to Flickr. So say they had a permissive license at first, then they see someone using their images for commercial purposes, and then they go and change the license of those images to be more restrictive (disable commercial use, for example). The person using the author's images used them when the license was permissive, but now the license is restrictive.

What happens in this situation? For any file type, or if that's too complex then I'm mainly interested in image/audio/video, or just images. Can the one using the author's file say "I started using it when the license was permissive, so I am free to use it now even though you changed the license"? Or what happens exactly in this situation, from a legal (and potentially practical) perspective? Must you take down the image after that?

If you are required to take down the image after you used it when it had a permissive license, that seems like pandora's box, and you can't trust any image, because what if someday they decide to make all their images restricted but you are using thousands of them from when the license was permissive?

Then there is the problem of proving the license was permissive at first, before it was changed. Flickr doesn't have license change logs, so maybe you would have to add the URL of the image to the wayback machine on archive.org to "prove" it was permissive? I don't get what you would have to do to make sure that, if you used an originally permissively licensed image/file, and then the license changed to more restrictive, that you won't get into trouble.

Answer 1

The creative commons licenses explicitly include a paragraph that they cannot be revoked once granted. That is an important concept of all free licenses (CC, but also MIT, Apache etc)

Now it's a fact that Flickr (and maybe other sites) do allow changing the license to something less permissive. If you use one of their images, it's really best to keep a proof that it once was available under the CC license you originally got it with. This can be e.g., a screenshot or a link to the wayback machine.

Wikimedia commons is often affected by this problem, as people regularly upload files from Flickr (which is absolutely ok, if they have a CC-by-sa or similar license at the time of the upload). Commons has installed a review process for such uploads. Trusted users check that the uploaded files really have the license on Flickr that the uploader declared. If later the license on Flickr is changed by the original owner, the history on Commons is considered to be enough evidence that the license was, in fact, permissive earlier. More about this can be read here.

Answer 2

You don’t mention a country, and I’m not a lawyer. I’d expect that you have the license that you received together with the copyrighted item you received, unless that license says under which circumstances the license can be withdrawn or changed, and that it cannot be changed retroactively.

If the license says it can be changed or withdrawn, and it is changed or withdrawn without you noticing, that’s your problem. But if this went to court, you could argue that damages can’t be that high if you do something today that you would have been allowed to do yesterday. Nevertheless, if the license can be changed at any time, that would be a reason not to use that copyrighted work.