my (simple) sudoers doesn't work

[Gauthier Vandemoortele <gauthier.v@skynet.be>]

Hello,

I wish to halt|shutdown| sleep my machine as an unprivilegied user on
the command-line or via the menu of a light window-manager.

Here's my /etc/sudoers

    Defaults        env_reset
    
    # User alias specification
    User_Alias     STOP = gv
    
    # Cmnd alias specification
    Cmnd_Alias     SLEEP = /usr/sbin/acpitool -S
    Cmnd_Alias     HALT = /usr/sbin/halt
    Cmnd_Alias     REBOOT = /usr/sbin/reboot
    
    # User privilege specification
    root    ALL=(ALL) ALL
    
    # Uncomment to allow members of group sudo to not need a password
    # (Note that later entries override this, so you might need to move
    # it further down)
    # %sudo ALL=NOPASSWD: ALL
    
    STOP ALL= NOPASSWD: SLEEP, HALT, REBOOT

The only thing I got to work is to insert

    gv ALL=(ALL) ALL

But in all other configurations,

    gv ALL = /usr/sbin/acpitool -S
    gv ALL = SLEEP

the response I get is:

    gv@fantasio:~$ sudo halt

    We trust you have received the usual lecture from the local System
    Administrator. It usually boils down to these three things:

        #1) Respect the privacy of others.
	#2) Think before you type.
	#3) With great power comes great responsibility.

   [sudo] password for gv: 
   Sorry, user gv is not allowed to execute '/sbin/halt' as
   root on fantasio.champignac.

What is the mistake ? (I use visudo and sudo 1.6.9p17-3 on Lenny)

Thanks in advance,
-- 
Gauthier

Les îles, c'est pas des îles,
au fond de l'eau, ça touche.
	(Brèves de comptoir - J-M Gourio)