polkit.addRule(
  function(action, subject) {
    if ( (action.id == "org.freedesktop.consolekit.reboot" ||
          action.id == "org.freedesktop.consolekit.reboot-multiple-sessions" ||
          action.id == "org.freedesktop.consolekit.power-off" ||
          action.id == "org.freedesktop.consolekit.power-off-multiple-sessions")
          && subject.isInGroup("power") ) {
      return polkit.Result.YES;
    }
  }
);