GitLab: Prevent Users From Accepting Their Pull Request

I have a group of developers working on a GitLab repository. I want all of them to be able to create merge requests, but I want to make sure there is a paper code review trail for every change, which means the merge request must be accepted by someone other than the author.

I can set up something that emulates this using a protected branch, but then only a subset of people can accept merge requests to that branch. This is unnecessarily restrictive; any code can be accepted as long as it passes the code check.

Is it possible to create such a workflow in GitLab? Specifically, is it possible to tweak things so that the user cannot accept their own Pull Request?