body: The original thread can be found here: [Stack Exchange and Stack Overflow are moving to CC BY-SA 4.0](https://meta.stackexchange.com/questions/333089/stack-exchange-and-stack-overflow-are-moving-to-cc-by-sa-4-0)
  
  
  As far as I understand, Stack Exchange can move on to CC BY-SA 4.0 for content published in the future, but they are not allowed to unilaterally change the license of previous publications. Several threads have been created requesting answers regarding this issue from Stack Exchange, however, [the only answer from moderator](https://meta.stackexchange.com/a/333912/619812) did not give any meaningful explanation. 
  
  
  Since this is a legal issue, I would like to ask of Law Stack Exchange community to give expert opinion on this matter.
  
  
  **Can Stack Exchange change the license for previously published content without the consent of users?**
  
  
  
title: Is Stack Exchange allowed to unilaterally change previously published content license?