Is it possible to edit the sudoers file so a user can use sudo for any command except for a specified one? I reverse is true, I believe, that the sudoers file can be setup so that a user can only execute a given list of commands.
EDIT: the commands I really want to take away are halt and reboot... this makes me think there are special system calls for halt and reboot. Can you take system calls away from a user? If not, is it because the unix permission system abstracts over system calls neglecting this?