Related Rule
Greece
Practice Relating to Rule 155. Defence of Superior Orders
The Hellenic Navy’s International Law Manual (1995) states:
The basic rules regulating the need for distinction between military and non-military targets and the obligation to restrict attacks only against the former create relevant duties and obligations incumbent not only on those responsible for the planning of the operations but also on those carrying them out. Therefore, a special international responsibility under international law is created for persons obeying unlawful orders or orders whose execution entails an illegitimate effect. Of course this attitude regarding individual criminal responsibility is not conventionally clear and bears a customary character, its legal justification being shaped from the jurisprudence of the Special Military Tribunal in Nuremberg which in 1945, in the context of the adjudication of the Einsatzgruppen case, applying the discretionary power vested upon it by art. 8 of its Statute, found that the existence of a disciplinary or criminally enforced obligation under national military codes for members of the armed forces to obey superior orders does not absolve them from criminal responsibility in cases they ought to have been aware of the criminal character of the orders received. 
Greece, International Law Manual, Hellenic Navy General Staff, Directorate A2, Division IV, 1995, Chapter 7, Part I, § 3.