Related Rule
United States of America
Practice Relating to Rule 72. Poison and Poisoned Weapons
The US Field Manual (1956) states: “It is especially forbidden … to employ poison or poisoned weapons.” 
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, § 37(a).
The manual further provides:
In addition to the “grave breaches” of the Geneva Conventions of 1949, the following acts are representative of violations of the law of war (“war crimes”):
making use of poisoned … arms or ammunition … [and] poisoning of wells or streams. 
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, § 504(a) and (i).
The US Air Force Pamphlet (1976) states: “A weapon may be illegal per se if either international custom or treaty has forbidden its use under all circumstances. An example is poison to kill or injure a person.” 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 6-2.
The Pamphlet further states: “Usage and practice has also determined that it is per se illegal … to use any substance on projectiles that tend unnecessarily to inflame the wound they cause.” 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 6-3b(2).
The Pamphlet defines poison as a “biological or chemical substance” and adds: “The long-standing customary prohibition against poison is based on their uncontrolled character and the inevitability of death or permanent disability.” 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 6-4f.
The US Soldier’s Manual (1984) instructs soldiers: “Using poison or poisoned weapons is against the law of war. You may not use poison or poisoning agents such as dead animals, bodies, or defecation to poison any water or food supply.” 
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. 10.
The US Instructor’s Guide (1985) provides: “In addition to the grave breaches of the Geneva Conventions, the following acts are further examples of war crimes: using poisoned … arms or ammunition [and] poisoning wells or streams.” 
United States, Instructor’s Guide – The Law of War, Headquarters Department of the Army, Washington, April 1985, p. 13.
The US Operational Law Handbook (1993) states that “using … poison weapons” is “expressly prohibited by the law of war” and is “not excusable on the basis of military necessity”. 
United States, Operational Law Handbook, JA 422, Center for Law and Military Operations and International Law Division, The Judge Advocate General’s School, United States Army, Charlottesville, Virginia 22903-1781, 1993, p. Q-182, § (i).
The US Naval Handbook (1995) states: “A few weapons, such as poisoned projectiles, are unlawful, no matter how employed.” 
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), § 9.1.
The US Manual for Military Commissions (2007), Part IV, Crimes and Elements, includes in the list of crimes triable by military commissions:
EMPLOYING POISON OR SIMILAR WEAPONS.
a. Text. “Any person subject to this chapter who intentionally, as a method of warfare, employs a substance or weapon that releases a substance that causes death or serious and lasting damage to health in the ordinary course of events, through its asphyxiating, bacteriological, or toxic properties, shall be punished, if death results to one or more of the victims, by death or such other punishment as a military commission under this chapter may direct, and, if death does not result to any of the victims, by such punishment, other than death, as a military commission under this chapter may direct.”
b. Elements.
(1) The accused intentionally employed a substance or a weapon that releases a substance as a result of its employment;
(2) The substance was such that causes death or serious damage to health in the ordinary course of events through its asphyxiating, poisonous, bacteriological properties;
(3) The accused employed the substance or weapon with the intent of utilizing such asphyxiating, poisonous, bacteriological properties as a method of warfare;
(4) The accused knew or should have known of the nature of the substance or weapon employed; and
(5) The conduct took place in the context of and was associated with armed conflict.
c. Comment.
(1) The “death or serious damage to health” required of the offense must be a direct result of the substance’s effect or effects on the human body (e.g., asphyxiation caused by the depletion of atmospheric oxygen secondary to a chemical or other reaction would not give rise to this offense).
(2) The clause “serious damage to health” does not include temporary incapacitation or sensory irritation.
(3) The use of the “substance or weapon” at issue must be proscribed under the law of armed conflict. It may include chemical or biological agents.
(4) The specific intent element for this offense precludes liability for mere knowledge of potential collateral consequences (e.g., mere knowledge of a secondary asphyxiating or toxic effect would be insufficient to complete the offense).
d. Maximum punishment. Death, if the death of any person occurs as a result of the employment of the substance or weapon. Otherwise, confinement for life. 
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 IV, § 6(8), pp. IV-6 and IV-7.
The US Naval Handbook (2007) states: “A few weapons, such as poisoned projectiles, are unlawful no matter how employed. Others may be rendered unlawful by alteration such as by coating ammunition with a poison.” 
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, § 9.1.
The US Manual for Military Commissions (2010), Part IV, Crimes and Elements, includes in the list of crimes triable by military commissions:
EMPLOYING POISON OR SIMILAR WEAPONS.
a. Text. “Any person subject to this chapter who intentionally, as a method of warfare, employs a substance or weapon that releases a substance that causes death or serious and lasting damage to health in the ordinary course of events, through its asphyxiating, bacteriological, or toxic properties, shall be punished, if death results to one or more of the victims, by death or such other punishment as a military commission under this chapter may direct, and, if death does not result to any of the victims, by such punishment, other than death, as a military commission under this chapter may direct.”
b. Elements.
(1) The accused intentionally employed a substance or a weapon that releases a substance as a result of its employment;
(2) The substance was such that causes death or serious damage to health in the ordinary course of events through its asphyxiating, poisonous, bacteriological properties;
(3) The accused employed the substance or weapon with the intent of utilizing such asphyxiating, poisonous, bacteriological properties as a method of warfare;
(4) The accused knew or should have known of the nature of the substance or weapon employed; and
(5) The conduct took place in the context of and was associated with hostilities.
c. Comment.
(1) The “death or serious damage to health” required of the offense must be a direct result of the substance’s effect or effects on the human body (e.g., asphyxiation caused by the depletion of atmospheric oxygen secondary to a chemical or other reaction would not give rise to this offense).
(2) The clause “serious damage to health” does not include temporary incapacitation or sensory irritation.
(3) The use of the “substance or weapon” at issue must be proscribed under the law of armed conflict. It may include chemical or biological agents.
(4) The specific intent element for this offense precludes liability for mere knowledge of potential collateral consequences (e.g., mere knowledge of a secondary asphyxiating or toxic effect would be insufficient to complete the offense).
d. Maximum punishment. Death, if the death of any person occurs as a result of the employment of the substance or weapon. Otherwise, confinement for life. 
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, § 5(8), pp. IV-7 and IV-8.
Under the US War Crimes Act (1996), violations of Article 23(a) of the 1907 Hague Regulations are war crimes. 
United States, War Crimes Act, 1996, Section 2441(c)(2).
The US Military Commissions Act (2006), passed by Congress following the Supreme Court’s decision in Hamdan v. Rumsfeld in 2006, amends Title 10 of the United States Code as follows:
§ 950v. Crimes triable by military commissions
“ …
“(b) OFFENSES.—The following offenses shall be triable by military commission under this chapter at any time without limitation:
“ …
“(8) EMPLOYING POISON OR SIMILAR WEAPONS.—Any person subject to this chapter who intentionally, as a method of warfare, employs a substance or weapon that releases a substance that causes death or serious and lasting damage to health in the ordinary course of events, through its asphyxiating, bacteriological, or toxic properties, shall be punished, if death results to one or more of the victims, by death or such other punishment as a military commission under this chapter may direct, and, if death does not result to any of the victims, by such punishment, other than death, as a military commission under this chapter may direct. 
United States, Military Commissions Act, 2006, Public Law 109-366, Chapter 47A of Title 10 of the United States Code, 17 October 2006, p. 120 Stat. 2626, § 950v(b)(8).
The US Military Commissions Act (2009) amends Chapter 47A of Title 10 of the United States Code as follows:
§ 950t. Crimes triable by military commission
“The following offenses shall be triable by military commission under this chapter at any time without limitation:
“ …
“(8) EMPLOYING POISON OR SIMILAR WEAPONS.—Any person subject to this chapter who intentionally, as a method of warfare, employs a substance or weapon that releases a substance that causes death or serious and lasting damage to health in the ordinary course of events, through its asphyxiating, bacteriological, or toxic properties, shall be punished, if death results to one or more of the victims, by death or such other punishment as a military commission under this chapter may direct, and, if death does not result to any of the victims, by such punishment, other than death, as a military commission under this chapter may direct. 
United States, Military Commissions Act, 2009, § 950t(8).
In 2008, in the Agent Orange case, the US Court of Appeals for the Second Circuit upheld the dismissal of the case by the District Court, finding that the Plaintiffs had failed to demonstrate a violation of international law. In its judgment, the Court of Appeals stated:
In support of their argument that the deployment of Agent Orange violated customary norms prohibiting use of “poisoned weapons” and the infliction of unnecessary suffering, Plaintiffs cite … a number of both domestic and international law sources … [including] the 1907 Hague Regulations … [and] the1925 Geneva [Gas] Protocol …
The United States did not ratify the 1925 Geneva Protocol until 1975. Accordingly, the Protocol cannot be said to have constituted “a treaty of the United States,” … during the period relevant to this appeal. Even at the time of ratification, the United States and other states reserved the right to respond in kind to a belligerent’s first use of poisonous weapons and further limited the treaty obligation to apply only against other treaty parties. … Given the nature and scope of the reservations to ratification, however, it would be an impermissible stretch to find that the 1925 Geneva Protocol had acquired the status of binding customary international law during the Vietnam conflict.
There is lack of a consensus in the international community with respect to whether the proscription against poison would apply to defoliants that had possible unintended toxic side effects, as opposed to chemicals intended to kill combatants. The prohibition on the use of “poison or poisoned weapons” in Article 23(a) of the 1907 Hague Regulations is certainly categorical … but its scope is nevertheless undefined and has remained so for a century. As the International Court of Justice (“ICJ”) has acknowledged in an authoritative interpretation of Article 23(a), that provision nowhere defines the critical term “poison,” and “different interpretations exist on the issue.” [Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion No. 95, 1996 I.C.J. 226, 248, 255 (July 8, 1996) (“Nuclear Weapons Advisory Opinion”)]. Indeed, Plaintiffs’ own expert conceded that “[t]he concept of ‘poison’ is not defined.” Plaintiffs themselves concede that the authorities “go both ways” as to whether the use of herbicides in war, “particularly to destroy crops not intended for use by enemy forces, did violate established norms of international law prior to 1975.”
… In 1969, the United States 7 objected to a proposed United Nations resolution that would have “ma[d]e a clear affirmation that the prohibition contained in the Geneva Protocol applied to the use in war of all chemical, bacteriological and biological agents (including tear gas and other harassing agents) which presently existed or which might be developed in the future.” The following year, after the United States ceased its use of Agent Orange upon a study revealing its deleterious effects on humans, the Secretary of State wrote a letter to President Nixon recommending that the President transmit to the Senate for advice and consent the ratification of the 1925 Geneva Protocol. In his letter, the Secretary stated that “[i]t is the United States’ understanding of the Protocol that it does not prohibit the use in war of riot-control agents and chemical herbicides.” When President Ford ratified the Geneva Protocol in 1975, he clarified that “[a]lthough it is our position that the [P]rotocol does not cover riot control agents and chemical herbicides, I have decided that the United States shall renounce their use in war as a matter of national policy.” Moreover, in ratifying the 1925 Geneva Protocol in 1975, the Senate made clear its understanding that the United States’ prior use of herbicides in Vietnam had not violated that treaty and that the government intended the Protocol to be only prospective in effect. 
United States, US Court of Appeals for the Second Circuit, Agent Orange case, Judgment, 22 February 2008, pp. 23–24, 27–28 and 30.
In 1974, in a memorandum on the depleted uranium tank round, the US Department of the Army stated: “The law of war prohibits the employment of poison or poisoned weapons.” 
United States, Department of the Army, Memorandum for US Army Research, Development and Engineering Center, M829A2 Cartridge, 120MM, APFSDS-T (Depleted Uranium Tank Round), Law of War Review, 27 December 1994, § 6(b).
In 1975, in a legal review of 30MM ammunition, the US Department of the Air Force stated: “Existing international law, both customary and treaty, prohibits the use of poison or poisoned weapons.” 
United States, Department of the Air Force, Legal Review of 30MM Ammunition, 14 March 1975, § II(1).
In its written statement submitted to the ICJ in the Nuclear Weapons case in 1995, the United States accepted the prohibition of poison as such. However, it considered the prohibition to be applicable only to “weapons that carry poison into the body of the victim” or “that are designed to kill or injure by the inhalation or other absorption into the body of poisonous gases or analogous substances”. 
United States, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, p. 24.