just cause; good reason; pretext; justification
duty (to one's country, sovereign, etc.)
それが大義名分なのか。
Is that really a just cause?
企業は環境保護を大義名分に掲げた。
The company put forward environmental protection as a just cause.
指導者は安全保障を大義名分に、その政策を正当化した。
The leader justified the policy, citing national security as a just cause.