Hi,
After googling a little bit I found 2 discussions in the xwiki mailing
lists, It describes a need similar to yours. Hope it will help.
http://lists.xwiki.org/pipermail/users/2005-December/000713.html
http://xwiki.475771.n2.nabble.com/how-to-approve-new-xwiki-users-td502460.h…
Regards,
Mohamed
On Fri, Jan 27, 2017 at 6:30 AM, Craig Wright <crw+xwiki(a)crw.xyz> wrote:
  Howdy,
 Is it possible to setup an XWiki such that:
 - Users can register AND validate email.
 - After registration, users who have not been “approved” can only see one
 page that says “Please wait for approval for access to this wiki."
 - Approved users have normal access controls.
 Right now I have removed all rights from the XWikiAllGroup and I manually
 move users into the XWikiRegisteredUsers group (maybe a bad name since all
 users are registered, it just means I approved them for access). The only
 problem with this setup is that new users cannot validate their email until
 I have added them to the XWikiRegisteredUsers group. I have not yet figured
 out how to control access to that special Email Authorization page.
  Thanks for any info!
 Craig