Manual:$wgRemoveGroups

From MediaWiki.org

Access: $wgRemoveGroups
Controls who can remove specifics groups using Special:Userrights.
Introduced in version:	1.11.0
Removed in version:	still in use
Allowed Values:	array
Default Value:	array()

Other settings: Alphabetical | By Function

[edit] Details

If a group can remove any right (example: bureaucrats can remove any right):

$wgRemoveGroups['bureaucrat'] = true;

If a group remove only some rights (example: bureaucrats can remove only sysop and bot groups):

$wgRemoveGroups['bureaucrat'] = array( 'sysop', 'bot' );

MediaWiki version:

1.12

and after

Note that groups which may only grant some rights (like bureaucrats in this example) need to have set userrights privilege to false, otherwise they will still be able to add all groups.