I've implemented a phpbb mod called Restricted Group.
- create the group and call it whatever you want.
 - make sure the group moderator can admin forums or the moderator will also be restricted.
 - in admin config you select that Restricted Group - no selection means no restriction.
 - any member added to that group immediately loses all privileges where the forum authorization levels are set to REG.
(affects view, read, post, reply, edit, delete, polls, vote, attach, download)
 - forums for which the member has group privileges will retain privileges.
 
Initiated by Bugger (Original Entry) - Comments Here Please.