public function user_delete($user) {
        global $DB;

        $sql = "SELECT e.*
                  FROM {enrol} e
                  JOIN {user_enrolments} ue ON (ue.enrolid = e.id)
                 WHERE e.enrol = :name AND ue.userid = :userid";
        $params = array('name'=>$this->get_name(), 'userid'=>$user->id);

        $rs = $DB->get_recordset_sql($sql, $params);
        foreach($rs as $instance) {
            $this->unenrol_user($instance, $user->id);
        }
        $rs->close();
    }