public function actionRevoke()
    {
        if (isset($_GET['itemName'], $_GET['userId'])) {
            $itemName = $_GET['itemName'];
            $userId = $_GET['userId'];

            /* @var $am CAuthManager|AuthBehavior */
            $am = Yii::app()->getAuthManager();

            if ($am->isAssigned($itemName, $userId)) {
                $am->revoke($itemName, $userId);
                if ($am instanceof CPhpAuthManager) {
                    $am->save();
                }

                if ($am instanceof ICachedAuthManager) {
                    $am->flushAccess($itemName, $userId);
                }
            }

            if (!isset($_POST['ajax'])) {
                $this->redirect(array('view', 'id' => $userId));
            }
        } else {
            throw new CHttpException(400, Yii::t('AuthModule.main', 'Invalid request.'));
        }
    }