normal user can shut down the system

[Kenny Hitt <kenny@hittsjunk.net>]

Hi.  I'm running the Gnome 2.6 on Sarge.  I just noticed a normal user
can choose to shutdown or reboot the system on logout.  How can I
disable such a stupid feature?  I'm sure this was discussed, but I can't
find the info.  Would someone please point me to a doc about this stupid
option and how to disable it?  Since the option is on the Gnome log out
dialog and I can't find anything about it in /etc/gdm.conf, it must be a
part of Gnome.

Thanks in advance.
          Kenny