It seems to me that SE holds contradictory positions:
So I'd like to understand how this is possible. Am I missing something? I'm not a lawyer but I'm pretty sure this isn't legal under a multiplicity of theories.
I own several books, movie tapes and music cassettes. I do not own the copyright of any of them.
No matter what the rightful copyright owners of those materials wish they can't delete my copies since I've acquired those copies legally. Surely you also would feel uncomfortable if copyright holders could delete your books.
SE has also acquired your content legally since you have agreed to the Terms of Service.
You agree that any and all content, including without limitation any and all text, graphics, logos, tools, photographs, images, illustrations, software or source code, audio and video, animations, and product feedback (collectively, “Content”) that you provide to the public Network (collectively, “Subscriber Content”), is perpetually and irrevocably licensed to Stack Overflow on a worldwide, royalty-free, non-exclusive basis pursuant to Creative Commons licensing terms (CC-BY-SA), and you grant Stack Overflow the perpetual and irrevocable right and license to access, use, process, copy, distribute, export, display and to commercially exploit such Subscriber Content, even if such Subscriber Content has been contributed and subsequently removed by you as reasonably necessary to, for example (without limitation).
- Provide, maintain, and update the public Network
- Process lawful requests from law enforcement agencies and government agencies
- Prevent and address security incidents and data security features, support features, and to provide technical assistance as it may be required
- Aggregate data to provide product optimization
This means that you cannot revoke permission for Stack Overflow to publish, distribute, store and use such content and to allow others to have derivative rights to publish, distribute, store and use such content. The CC-BY-SA Creative Commons license terms are explained in further detail by Creative Commons, but you should be aware that all Public Content you contribute is available for public copy and redistribution, and all such Public Content must have appropriate attribution.
As stated above, by agreeing to these Public Network Terms you also agree to be bound by the terms and conditions of the Acceptable Use Policy incorporated herein, and hereby acknowledge and agree that any and all Public Content you provide to the public Network is governed by the Acceptable Use Policy.
SE only loses the rights conferred by that agreement if the agreement becomes invalid. Like in the case of a violation of the agreement by SE.
Owning the copyright to something is what gives you the right to license that thing for use to someone else. Using your question as an example, what SE is saying is that you own the copyright to that question. You have control over who you license that text to. Since SE does not open the copyright to it, they cannot stop you from doing whatever you want. You could paint it onto a billboard in Times Square, publish it as a Kindle book, or upload it to github. Go wild!
What SE is saying is that by posting here, you are also implicitly licensing it to SE under (as of now) cc by-sa 4.0. This gives SE limited rights to that content. Those limited rights are the right to edit the text in any way (which would include restoring it if you deleted it.) The limits to these rights are that they must always attach your name to it, and always make clear if your original post was edited.
So basically their position is that you can do whatever you want to the text and that they can distribute both original and edited versions of it on their site. That is not contradictory.
