Board Thread:Support Requests - Community Management/@comment-4902297-20130226055138/@comment-3335785-20130226112958

Assuming Wikia are removing user-right due to inactivity at the request of a wiki, then they can get them back by the usual methods, such as another bureaucrat bureaucratting them, or staff will if they have evidence of a discussion.

If they have been removed as a result of abuse where staff have had to step in, I believe it's still technically possible, but I don't think they're allowed them. Whether there's any system that prevents you doing this, I don't know.