Related Rule
United States of America
Practice Relating to Rule 155. Defence of Superior Orders
The US Field Manual (1956) provides:
The fact that the law of war has been violated pursuant to an order of a superior authority, whether military or civil, does not deprive the act in question of its character of a war crime, nor does it constitute a defense in the trial of an accused individual, unless he did not know and could not reasonably have been expected to know that the act ordered was unlawful. In all cases where the order is held not to constitute a defense to an allegation of war crime, the fact that the individual was acting pursuant to orders may be considered in mitigation of punishment. 
United States, Field Manual 27-10, The Law of Land Warfare, US Department of the Army, 18 July 1956, as modified by Change No. 1, 15 July 1976, § 509(a).
The US Air Force Pamphlet (1976) provides:
The fact that an act was committed pursuant to military orders is an acceptable defense only if the accused did not know or could not reasonably have been expected to know that the act ordered was unlawful … Nevertheless, in all cases, the fact that an individual was acting pursuant to orders may be considered a mitigating factor in determining punishment. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 15-4(d).
The manual gives the example of the Manual for Courts-Martial, which states:
An order requiring the performance of a military duty may be inferred to be legal. An act performed manifestly beyond the scope of authority, or pursuant to an order that a man of ordinary sense and understanding would know to be illegal, or in a wanton manner discharge of a lawful duty, is not excusable. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 15-4(d).
The US Soldier’s Manual (1984) tells soldiers:
Even if you had orders to commit the act, you are personally responsible. Orders are not a defense.
Soldiers who kill captives or detainees cannot excuse themselves from the acts by claiming that an order to “take care of” a captive or detainee was understood to mean “execution”. Common sense and the laws of war will help you recognize what is clearly criminal. 
United States, Your Conduct in Combat under the Law of War, Publication No. FM 27-2, Headquarters Department of the Army, Washington, November 1984, p. 26.
The US Naval Handbook (1995) states:
Under both international law and US law, an order to commit an obviously criminal act, such as the wanton killing of a noncombatant or the torture of a prisoner, is an unlawful order and will not relieve a subordinate of his responsibility to comply with the law of armed conflict. Only if the unlawfulness of an order is not known by the individual, and he could not reasonably be expected under the circumstances to recognize the order as unlawful, will the defense of obedience of an order protect a subordinate from the consequences of violation of the law of armed conflict. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-2.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Transportation, US Coast Guard, October 1995 (formerly NWP 9 (Rev. A)/FMFM 1-10, October 1989), § 6.1.4.
[emphasis in original]
The manual further states:
The fact that a person committed a war crime under orders of his military or civilian superior does not relieve him from responsibility under international law. It may be considered in mitigation of punishment. To establish responsibility, the person must know (or have reason to know) that an act he is ordered to perform is unlawful under international law. Such an order must be manifestly illegal. The standard is whether under the same or similar circumstances a person of ordinary sense and understanding would know the order to be unlawful. If the person knows the act is unlawful and only does it under duress, this circumstance may be taken into consideration either by way of defense or in mitigation of punishment. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-2.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Transportation, US Coast Guard, October 1995 (formerly NWP 9 (Rev. A)/FMFM 1-10, October 1989), § 6.2.5.5.1.
The Annotated Supplement to the US Naval Handbook (1997) states: “Under both international law and U.S. law, an order to commit an obviously criminal act … is an unlawful order and will not relieve the subordinate of his responsibility to comply with the law of armed conflict.” It specifies: “The order may be direct or indirect, explicit or implied.” 
United States, Annotated Supplement to the Commander’s Handbook on the Law of Naval Operations, prepared by the Oceans Law and Policy Department, Center for Naval Warfare Studies, Naval War College, Newport, Rhode Island, November 1997, § 6.1.4 and footnote 16.
The US Manual for Military Commissions (2007) states:
Obedience to orders. It is a defense to any offense that the accused was acting pursuant to orders unless the accused knew the orders to be unlawful or a person of ordinary sense and understanding would have known the orders to be unlawful. 
United States, Manual for Military Commissions, published in implementation of the Military Commissions Act of 2006, 10 U.S.C. §§ 948a, et seq., 18 January 2007, Part II, Rule 916 (d), p. IV-1.
The US Naval Handbook (2007) states:
Under both international law and U.S. law, an order to commit an obviously criminal act, such as the wanton killing or torture of a prisoner, is an unlawful order and will not relieve a subordinate of his responsibility to comply with the law of armed conflict. Only if the unlawfulness of an order is not known by the individual, and he could not reasonably be expected under the circumstances to recognize the order as unlawful, will the defense of obedience to an order protect a subordinate from the consequences of violating the law of armed conflict. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-12.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Homeland Security, US Coast Guard, July 2007, § 6.1.4.
[emphasis in original]
The Handbook also states:
The fact that a person committed a war crime under orders of his military or civilian superior does not by itself relieve him of criminal responsibility under international law. It may, however, be considered in mitigation of punishment. To establish responsibility, the person must know (or have reason to know) that an act he is ordered to perform is unlawful under international law. Such an order must be manifestly illegal. The standard is whether under the same or similar circumstances a person of ordinary sense and understanding would know the order to be unlawful. If the person knows the act is unlawful and only does it under duress, this circumstance may be taken into consideration either by way of defense or in mitigation of punishment. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-12.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Homeland Security, US Coast Guard, July 2007, § 6.2.6.4.1.
The US Manual for Military Commissions (2010) states: “Obedience to orders. It is a defense to any offense that the accused was acting pursuant to orders unless the accused knew the orders to be unlawful or a person of ordinary sense and understanding would have known the orders to be unlawful.” 
United States, Manual for Military Commissions, published in implementation of Chapter 47A of Title 10, United States Code, as amended by the Military Commissions Act of 2009, 10 U.S.C, §§ 948a, et seq., 27 April 2010, Rule 916, p. II-113.
The US Detainee Treatment Act (2005) states:
Sec. 1004. Protection of United States Government Personnel Engaged in Authorized Interrogations.
(a) Protection of United States Government Personnel – In any civil action or criminal prosecution against an officer, employee, member of the Armed Forces, or other agent of the United States Government who is a United States person, arising out of the officer, employee, member of the Armed Forces, or other agent’s engaging in specific operational practices, that involve detention and interrogation of aliens who the President or his designees have determined are believed to be engaged in or associated with international terrorist activity that poses a serious, continuing threat to the United States, its interests, or its allies, and that were officially authorized and determined to be lawful at the time that they were conducted, it shall be a defense that such officer, employee, member of the Armed Forces, or other agent did not know that the practices were unlawful and a person of ordinary sense and understanding would not know the practices were unlawful. Good faith reliance on advice of counsel should be an important factor, among others, to consider in assessing whether a person of ordinary sense and understanding would have known the practices to be unlawful.  
United States, Detainee Treatment Act, 2005, Title X of Public Law 109-148 (the 2006 Department of Defense Appropriations Act), 119 Stat 2680, 30 December 2005, § 1004(a).
In its judgment in the Klein case (The Hadamar Trial) in 1945, the US Military Commission in Wiesbaden applied to the relationship of civilian employees to their superiors the doctrine that individuals who violate the laws and customs of war are criminally liable in spite of their acting under a superior order, if the order was illegal. 
United States, Military Commission in Wiesbaden, Klein case (The Hadamar Trial), Judgment, 8–15 October 1945.
In the Krupp case in 1947/48, in which Alfried Krupp and eleven others were charged with having employed prisoners of war, forced labour and inmates of concentration camps in the German war industry, the US Military Tribunal at Nuremberg, in response to the argument of the defence that the accused had acted according to the Reich policies and to an order requiring certain production quota and that, if they had refused to do so, they would have suffered dire consequences, stated:
The real defense in this case … is that of necessity … Under the rule of necessity, the contemplated compulsion must actually operate upon the will of the accused to the extent he is thereby compelled to do what otherwise he would not have done … Here we are not dealing with necessity brought about by circumstances independent of human agencies or by circumstances due to accident or misadventure. On the contrary, the alleged compulsion relied upon is said to have been exclusively due to the certainty of loss or injury at the hands of an individual or individuals if their orders were not obeyed. In such cases, if, in the execution of the illegal act, the will of the accused be not thereby overpowered but instead coincides with the will of those from whom the alleged compulsion emanates, there is no necessity justifying the illegal act. 
United States, Military Tribunal at Nuremberg, Krupp case, Judgment, 17 November 1947–30 June 1948.
In its judgment in the Krauch case (The I.G. Farben Trial) in 1947/48 in which leading German industrials were charged with employment of POWs, forced labour and concentration camp inmates in illegal work and under inhuman conditions, the US Military Tribunal at Nuremberg stated:
The IMT [International Military Tribunal] recognized that while an order emanating from a superior officer or from the government is not, of itself, a justification for the violation of an international law (though it may be considered in mitigation), nevertheless, such an order is a complete defense where it is given under such circumstances as to afford the one receiving it no other moral choice than to comply therewith. As applied to the facts here, we do not think there can be much uncertainty as to what the words “moral choice” mean. 
United States, Military Tribunal at Nuremberg, Krauch case (The I.G. Farben Trial), Judgment, 14 August 1947–29 July 1948.
In the Griffen case in 1968, a US Army Board of Review approved the decision of the trial law officer who refused to give an instruction to the panel on the defence of obedience of orders, considering that an order to kill an unarmed and unresisting prisoner was “so palpably illegal on its face” that this defence was not an issue. 
United States, Army Board of Review, Griffen case, Judgment, 2 July 1968.
In the Calley case in 1973, the US Army Court of Military Appeals approved the following instructions given to the panel by the trial judge in a case where the accused invoked an order to kill unresisting detainees:
The acts of a subordinate done in compliance with an unlawful order given him by his superior are excused and impose no criminal liability upon him unless the superior’s order is one which a man of ordinary sense and understanding would, under the circumstances, know to be unlawful, or if the order in question is actually known to the accused to be unlawful. 
United States, Army Court of Military Appeals, Calley case, Judgment, 21 December 1973.
[emphasis in original]
Citing a writer’s opinion, the Court stated:
For the inferior to assume to determine the question of the lawfulness of an order given him by a superior would of itself, as a general rule, amount to insubordination, and such an assumption carried into practice would subvert military discipline. Where the order is apparently regular and lawful on its face, he is not to go behind it to satisfy himself that his superior has proceeded with authority, but is to obey it according to its terms, the only exceptions recognized to the rule of obedience being cases of orders so manifestly beyond the legal power or discretion of the commander as to admit of no rational doubt of their unlawfulness
Except in such instances of palpable illegality, which must be of rare occurrence, the inferior should presume that the order was lawful and authorized and obey it accordingly, and in obeying it can scarcely fail to be held justified by a military court. 
United States, Army Court of Military Appeals, Calley case, Judgment, 21 December 1973, referring to Col. William Winthrop, Military Law and Precedents, pp. 296–297, 2nd edition 1920 (reprint).
[emphasis in original]
In his dissenting opinion in the Calley case in 1973, one of the judges stated:
My impression is that the weight of authority … supports a more liberal approach to the defense of superior orders. Under this approach, superior orders should constitute a defense except “in a plain case of excess of authority, where at first blush it is apparent and palpable to the commonest understanding that the order is illegal”.
While this test is phrased in language that now seems “somewhat archaic and ungrammatical”, the test recognizes that the essential ingredient of discipline in any armed force is obedience to orders and that this obedience is so important it should not be penalized unless the order would be recognized as illegal, not by what some hypothetical reasonable soldier would have known, but also by “those persons at the lowest end of the scale of intelligence and experience in service”. This is the real purpose in permitting superior orders to be a defense, and it ought not to be restricted by the concept of a fictional reasonable man so that, regardless of his personal characteristics, an accused judged after the fact may find himself punished for either obedience or disobedience, depending on whether the evidence will support the finding of simple negligence on his part …
Because the original case language is archaic and somewhat ungrammatical, I would rephrase it to require that the military jury be instructed that, despite his asserted defense of superior orders, an accused may be held criminally accountable for his acts, allegedly committed pursuant to such orders, if the court members are convinced beyond a reasonable doubt (1) that almost every member of the armed forces would have immediately recognized that the order was unlawful, and (2) that the accused should have recognized the order’s illegality as a consequence of his age, grade, intelligence, experience, and training. 
United States, Army Court of Military Appeals, Calley case, Dissenting opinion of Judge Darden, 21 December 1973.
The Agent Orange case in 2005 involved a class action suit filed on behalf of various Vietnamese nationals and an organization, The Vietnamese Association for Victims of Agent Orange/Dioxin, against Dow Chemical and other US chemical manufacturers, for harms allegedly done to them and their land through the United States’ use of Agent Orange and other herbicides during the Vietnam War from 1965 to 1971 and by the South Vietnamese government’s subsequent use of such herbicides until 1975. In dismissing the claims, the Court found that, while recognizing the evolution of international law since 1975, the use of herbicides did not violate, at the time they were used, either customary or conventional international law binding on the United States. With regard to the defence of necessity, the Court stated:
[T]he concerns of the United States about the terms of the Statute of the International Criminal Court, adopted in Rome on July 17, 1998, based on solicitude for soldiers who have to decide in the heat of battle whether to obey an order which may violate human rights, as suggested in the discussion of proportionality infra Part XI.D.3., is quite different from that of a corporation which can consult counsel and reflect before following an illegal order to supply products to be used to harm people in violation of international law. See, e.g., L. Doswald-Beck, The Value of the 1977 Geneva Protocols for the Protection of Civilians, in ARMED CONFLICT AND THE NEW LAW: ASPECTS OF THE 1977 GENEVA PROTOCOLS AND THE 1981 WEAPONS CONVENTION 137, 149-50 (Michael A. Meyer, ed., 1989) (discussing special problems in guerilla warfare where combatants may hide among civilians); Paola Gaeta, The Defence of Superior Orders: The Statute of the International Criminal Court Versus Customary International Law, 10 EUR. J. INT’L L. 172 (1999); Charles Garraway, Superior Orders and the International Criminal Court: Justice Delivered or Justice Denied, INT’L REV. OF THE RED CROSS, No. 836, at 785 (1999) …
Defendants in the case at bar were ordered by the government to produce as much Agent Orange as they could and to promptly deliver it to the government. Such a commercial order, even in wartime, hardly constitutes “necessity” under domestic or international law.
We are a nation of free men and women habituated to standing up to government when it exceeds its authority. See, e.g., Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579 (1952) (holding that seizure of steel mill during a war on an order of the President “to avert a national catastrophe” in his position as Commander-in-Chief of the armed forces exceeded his constitutional power). Under the circumstances of the present case, necessity is no defense. If defendants were ordered to do an act illegal under international law they could have refused to do so, if necessary by abandoning their businesses. 
United States, Eastern States District Court (EDNY), Agent Orange case, Judgment, 28 March 2005, pp. 154–157.
[emphasis in original]
At the CDDH, the United States submitted an amendment relative to Article 77 of the draft Additional Protocol I which read:
Delete the word “grave” from paragraph 1.
Amend paragraph 2 to read:
“The fact of having acted pursuant to an order of his government or of a superior does not absolve an accused person from responsibility if it be established that, in the circumstances at the time, he knew or should have known that he was committing a breach of the Conventions or of the present Protocol. The fact that the individual was acting pursuant to orders may, however, be taken into account in mitigation of punishment.” 
United States, Amendment submitted to the CDDH concerning Article 77 of the draft Additional Protocol I, CDDH, Official Records, Vol. III, CDDH/I/308, 27 April 1976, p. 332.
In 1993, during a debate in the UN Security Council following the unanimous vote on Resolution 827 (1993) establishing the International Criminal Tribunal for the former Yugoslavia (ICTY), the United States stated that under Article 7 of the 1993 ICTY Statute “it is, of course, a defence that the accused was acting pursuant to orders where he or she did not know the orders were unlawful and a person of ordinary sense and understanding would not have known the orders to be unlawful”. 
United States, Statement before the UN Security Council, UN Doc. S/PV.3217 (Provisional), 25 May 1993, p. 16.