Noun
(ethics, international law, idiomatic) An explanation offered as an excuse for behaving in a criminal or wrongful manner, claiming that one acted in this way because one was ordered by others (particularly superiors) to do so.
Synonyms: lawful orders, superior orders
(US law, by extension) An explanation offered as a defense to criminal or wrongful behavior, claiming that one is justified in not obeying a governmental order or a domestic law because the order or law is itself unlawful.
Source: en.wiktionary.org