Craft\WorkflowController::actionRejectSubmission PHP Method

    public function actionRejectSubmission()
    {
        $user = craft()->userSession->getUser();
        $draftId = craft()->request->getParam('draftId');
        $submissionId = craft()->request->getParam('submissionId');
        $notes = craft()->request->getParam('notes');
        $model = craft()->workflow_submissions->getById($submissionId);
        $model->status = Workflow_SubmissionModel::REJECTED;
        $model->publisherId = $user->id;
        $model->dateRejected = new DateTime();
        $model->notes = $notes;
        if (craft()->workflow_submissions->rejectSubmission($model)) {
            craft()->userSession->setNotice(Craft::t('Submission rejected.'));
        } else {
            craft()->userSession->setError(Craft::t('Could not reject submission.'));
        }
        // Redirect page to the entry as its not a form submission
        craft()->request->redirect(craft()->request->urlReferrer);
    }