Règle correspondante
Italy
Practice Relating to Rule 154. Obedience to Superior Orders
Italy’s IHL Manual (1991) states:
Concerning the norm and the consequent disciplinary rule, “the soldier who is requested to obey an order which manifestly violates State institutions or an order whose execution would anyway constitute a manifest crime, is under the obligation not to execute that order and inform his superiors as soon as possible. 
Italy, Manuale di diritto umanitario, Introduzione e Volume I, Usi e convenzioni di Guerra, SMD-G-014, Stato Maggiore della Difesa, I Reparto, Ufficio Addestramento e Regolamenti, Rome, 1991, Vol. I, § 83.
In its judgment in the Hass and Priebke case in 1997, Italy’s Military Tribunal of Rome stated that the duty to disobey an openly criminal order was independent from the fact that the subordinate could or could not prevent the event. The Tribunal further stated: “It is evident, indeed, that a member of the armed forces must not obey an unlawful order given to him even if he is aware that other persons may be willing to carry it out.” 
Italy, Military Tribunal of Rome, Hass and Priebke case, Judgment in Trial of First Instance, 22 July 1997.
In its relevant parts, this judgment was confirmed by the Military Appeals Court and the Supreme Court of Cassation. 
Italy, Military Appeals Court, Hass and Priebke case, Judgment on Appeal, 7 March 1998; Supreme Court of Cassation, Hass and Priebke case, Judgment in Trial of Third Instance, 16 November 1998.
On the basis of the decisions of the Military Tribunal of Rome in the Priebke case and in the Hass and Priebke case, the Report on the Practice of Italy concludes that “the opinio juris of Italy is that a soldier has the duty to disobey an order to commit a violation of international humanitarian law”. 
Report on the Practice of Italy, 1997, Chapter 6.8.