not open to discussion; there is no point in arguing about it; not up for debate.
安全上の理由で立ち入りは問答無用です。
For safety reasons, entry is not up for discussion.
上司の命令は問答無用に従わなければならない場合がある。
There are times when you must follow a boss's order without question.
その提案は問答無用で却下された。
That proposal was dismissed without discussion.