Thread:Project:Support desk/Group permissions have no effect/reply (3)

You can take permissions away either by not granting them (read as: not granting them to any of the user's groups).

The other, the better way, would to revoke them using $wgRevokePermissions: This allows to take permissions away. Now you only need to check, if there is a permission for viewing of special pages; I don't know that off-hand.