Admin Forum:Only allowing owner (or admin) approved users to edit?

I was wondering if it's possible to make it so that the owner (or all of the admins) has control over who can edit. As in, you cannot edit the wiki unless someone has explicitly added you to a whitelist of some kind. http://help.wikia.com/wiki/Help:User_access_levels doesn't seem to explicitly say how to do something like this, but even making it so that only admins can edit at all would be good enough.

Is this possible on wikia, or would I have to go to some other wiki service like wikispaces? (http://community.wikia.com/wiki/Admin_Forum:How_to_make_a_wikia_for_registered_users_only?t=20120627165024 doesn't make me optimistic)
 * According to Terms of Use, its not possible. -- http://i151.photobucket.com/albums/s145/urbancowgurl777/UltimateSupreme2212-3.png  (Talk to me) 14:11, July 26, 2012 (UTC)