Board Thread:Support Requests - Getting Started/@comment-24205722-20150410171045/@comment-4018164-20150410173335

To begin with, the user rights which cannot be removed are his bureaucrat- since only staff members can do that. Based on why you'd like to demote him, it might also be good to add a project page with a list of users from all groups and their status (e.g. active/inactive/away), or to add an "Inactive" user badge to their profile, like what UserTags. This way people who search for users in certain groups will be able to find them easily, and pick one that is active. It seems like your wiki already has a page for listing admins, so you could just add a status there.

If you'd still like to remove the rights of this user, unless he he's brutally broken the wiki's rules or the terms of use, the only way the staff accept a right removal request is by holding a community vote, and when done, send the results to Special:Contact/general.