Related Rule
Israel
Practice Relating to Rule 154. Obedience to Superior Orders
Israel’s Manual on the Rules of Warfare (2006) states:
[U]nder Israeli law … a soldier who has carried out an unlawful order will not be charged with an offence. Only if the order itself is patently unlawful is he required not to perform it, and indeed, under Israeli law, he would have no defence if he did execute it. 
Israel, Rules of Warfare on the Battlefield, Military Advocate-General’s Corps Command, IDF School of Military Law, Second Edition, 2006, p. 46.
The Manual on the Rules of Warfare (2006) is a second edition of the Manual on the Laws of War (1998).
In the Ofer, Malinki and Others case in 1958, Israel’s District Military Court for the Central Judicial District stated:
The rule is that a soldier must obey every order (subject to the exception) given him by his commander while fulfilling his duty … The exception is that he need not execute an order that is manifestly illegal.
As to the term “manifestly illegal”, the Court went on to explain that:
The identifying mark of a “manifestly unlawful” order must wave like a black flag above the order given, as a warning saying: “forbidden”. It is not formal unlawfulness, hidden or half-hidden, not unlawfulness that is detectable only by legal experts, that is the important issue here, but an overt and salient violation of the law, a certain and obvious unlawfulness that stems from the order itself, the criminal character of the order itself or of the acts it demands to be committed, an unlawfulness that pierces the eye and agitates the heart, if the eye be not blind nor the heart closed or corrupt. That is the degree of “manifest” illegality required in order to annul the soldier’s duty to obey and render him criminally responsible for his actions. 
Israel, District Military Court for the Central Judicial District, Ofer, Malinki and Others case, Judgment, 13 October 1958.
The Military Court of Appeal adopted these words and added that the legislator’s solution to the problem of conflict between law and obedience is, as it were, a golden mean between giving complete preference to one of those factors over the other, because it recognized
the impossibility of reconciling these two values through purely formal law, and therefore foregoes the attempt to resolve the problem by these means alone; it bursts out of the confines, as it were, of the purely judicial categories, calling for help on the sense of lawfulness that lies deep within the conscience of every human being as such, even if he is not expert in the law. 
Israel, Military Court of Appeal, Ofer, Malinki and Others case, Judgment, 3 April 1959.
At the CDDH, Israel stated that it had voted in favour of Article 77 of the draft Additional Protocol I and that:
The article is a reflection of existing customary international law clearly enunciated in the Nürnberg principles and embodied in [Israeli law].
We regret that Article 77 was not adopted … and wish to state that the rule [initially providing, inter alia, that “no person shall be punished for refusing to obey an order of his government or of a superior which, if carried out, would constitute a grave breach of the provisions of the Conventions or of the present Protocol”] continues to be governed by customary international law. 
Israel, Statement at the CDDH, Official Records, Vol. VI, CDDH/SR.45, 30 May 1977, p. 336.
The Report on the Practice of Israel states:
Under general Israeli law and IDF [Israeli Defense Forces] internal regulations, there exists a differentiation between an “unlawful order” and a “manifestly unlawful order”. Based on the understanding that clarity of command is a required element in any military organization, all IDF soldiers are required to comply with “unlawful orders” … As regards “manifestly unlawful orders” … IDF soldiers are required by law to refuse any such order. 
Report on the Practice of Israel, 1997, Chapter 6.8.