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