There is a security role permission titled "Always Edit Articles" for the Knowledge Base. This allows them to edit any article for any reason without needing any approval for the changes to take immediate effect.
You would have to find the security role that those users have, and take that option away from the role as a whole. Meaning, anyone assigned to that security role would not have that permission the next time they signed in. It cannot be controlled on a user-by-user basis at this time.
I hope this has explained how user permissions for the Knowledge Base can be modified. If you have any further questions on this please let me know.