Related Rule
United States of America
Practice Relating to Rule 137. Participation of Child Soldiers in Hostilities
The US Intelligence Reform and Terrorism Prevention Act (2004), states in Title VII—Implementation of 9/11 Commission Recommendations; Subtitle A—Diplomacy, Foreign Aid, and the Military in the War on Terrorism
Sec. 7104. Assistance for Afghanistan.
(h) UNITED STATES POLICY TO SUPPORT DISARMAMENT OF PRIVATE MILITIAS AND EXPANSION OF INTERNATIONAL PEACEKEEPING AND SECURITY OPERATIONS IN AFGHANISTAN.—
(1) UNITED STATES POLICY RELATING TO DISARMAMENT OF PRIVATE MILITIAS.—
(A) IN GENERAL.—It shall be the policy of the United States to take immediate steps to provide active support for the disarmament, demobilization, and reintegration of armed soldiers, particularly child soldiers, in Afghanistan, in close consultation with the President of Afghanistan. 
United States, Intelligence Reform and Terrorism Prevention Act, 2004, Public Law 108-458, 17 December 2004, Title V, Subtitle E, § 7104(h)(1)(A).
The US Child Soldiers Accountability Act (2008) amends Chapter 118 of Title 18 of the United States Code as follows:
“§ 2442. … use of child soldiers
“(a) OFFENSE.—Whoever knowingly–
“(2) uses a person under 15 years of age to participate actively in hostilities;
knowing such person is under 15 years of age, shall be punished as provided in subsection (b).
“(b) PENALTY.—Whoever violates, or attempts or conspires to violate, subsection (a) shall be fined under this title or imprisoned not more than 20 years, or both and, if death of any person results, shall be fined under this title and imprisoned for any term of years or for life.
“(d) DEFINITIONS.—In this section:
“(1) PARTICIPATE ACTIVELY IN HOSTILITIES.—The term ‘participate actively in hostilities’ means taking part in—
“(A) combat or military activities related to combat, including sabotage and serving as a decoy, a courier, or at a military checkpoint; or
“(B) direct support functions related to combat, including transporting supplies or providing other services.
“(2) ARMED FORCES OR GROUP.—The term ‘armed force or group’ means any army, militia, or other military organization, whether or not it is state-sponsored, excluding any group assembled solely for non-violent political association.” 
United States, Child Soldiers Accountability Act, 2008, § 2442(a), (b) and (d)(1) and (2).
In 1987, the deputy legal adviser of the US Department of State affirmed: “We support … the principle that … all feasible measures be taken in order that children under the age of fifteen do not take a direct part in hostilities.” 
United States, Remarks of Michael J. Matheson, Deputy Legal Adviser, US Department of State, The Sixth Annual American Red Cross-Washington College of Law Conference on International Humanitarian Law: A Workshop on Customary International Law and the 1977 Protocols Additional to the 1949 Geneva Conventions, American University Journal of International Law and Policy, Vol. 2, 1987, p. 428.
In 1996, during a debate in the UN Security Council on the situation in Liberia, the United States stated that “the era of the child soldier in Liberia must come to an end immediately” and that it “is an outrage by any standard of civilization that children under the age of 15, numbering between 4,000 and 6,000, are toting automatic weapons, slaughtering innocent civilians and ignoring the rule of law”. It denounced again what it called this “abhorrent practice”. 
United States, Statement before the UN Security Council, UN Doc. S/PV.3694, 30 August 1996, pp. 5 and 15.
According to the Report on US Practice, “Articles 4, 5 and 6 [of the 1977 Additional Protocol II] reflect general US policy on treatment of persons in the power of an adverse party in armed conflicts governed by common Article 3” of the 1949 Geneva Conventions. The report also notes: “It is the opinio juris of the US that persons detained in connection with an internal armed conflict are entitled to humane treatment as specified in Articles 4, 5 and 6 [of the 1977 Additional Protocol II].” 
Report on US Practice, 1997, Chapter 5.3.
In 2005, in its third periodic report to the Human Rights Committee, the United States stated:
Prior to U.S. ratification of the Optional Protocol to the Convention on the Rights of the Child on [the Involvement of] Children in Armed Conflict [which came into effect for the United States on 23 January, 2003], it was the practice of the U.S. Department of Defense that individuals under the age of 18 should not be stationed in combat situations. See Regular Army and Army Reserve Enlistment Program, Army Regulation 601-210, Headquarters, Department of the Army, 1 December 1988, Chapter 2. However, coincident with ratification of the Optional Protocol, each branch of the U.S. military has adopted policies that fulfill the obligation assumed by the United States under the Optional Protocol that all feasible measures should be taken to ensure that persons under the age of 18 do not take a direct part in hostilities. 
United States, Third periodic report to the Human Rights Committee, 29 November 2005, UN Doc. CCPR/C/USA/3, § 378.
In 2007, in its initial report to the Committee on the Rights of the Child under the 2000 Optional Protocol on the Involvement of Children in Armed Conflict, the United States stated:
To implement the terms of Article 1 of the Protocol, U.S. Military Services have adopted an implementation plan. The implementation plans have been tailored to meet the unique mission requirements of each Service. The implementation plans went into effect in January 2003. The plans relate to the date (not year) of birth of the individual. Summaries of each Service implementation plan … follow:
Army. The Army will not assign soldiers outside the United States, either on permanent or temporary duty orders, until they reach their eighteenth birthdate. For those soldiers under eighteen who were already overseas at the time the implementation plan went into effect, commanders were to take all feasible measures to ensure these soldiers not take a direct part in hostilities until they reached 18 years of age.
Navy. Sailors who have not reached their eighteenth birthdate will not be assigned to ships and squadrons that are scheduled to deploy at a date earlier than their eighteenth birthday.
Air Force. The Air Force will not assign airmen who have not reached their eighteenth birthdate to hostile fire/imminent danger areas.
Marine Corps. The Marine Corps has directed commanders who have operational and administrative control of Marines who have not reached their eighteenth birthdate to track and manage the assignment of those Marines such that all feasible measures are taken to ensure they do not take a direct part in hostilities. This responsibility may not be delegated below the battalion or squadron commander level. 
United States, Initial Report to the Committee on the Rights of the Child under the Optional Protocol on the Involvement of Children in Armed Conflict, U.N. Doc. CRC/C/OPAC/USA/1 (2007), 22 June 2007, submitted on 8 May 2007, § 17.
In May 2008, in a joint press briefing given in Geneva by the US Ambassador-at-Large and Director, Office to Monitor and Combat Trafficking in Persons, and by the Deputy Assistant Secretary, Detainee Affairs, Department of Defense, the Defense representative stated:
[T]he vast majority of all individuals who do voluntarily serve in the [US] military are 18 or older when they begin; more than 90 percent.
Even within that category for those who are 17, generally their training is concluded by the time they hit their 18th birthday, and in the instances where it is not we have put in effect policies that take all feasible measures to ensure that no one at the age of 17 takes direct participation in hostilities.
So as part of our acceding to this protocol [2000 Optional Protocol on the Involvement of Children in Armed Conflict] and taking this responsibly, we’ve gone through a number of revisions to the way in which we use our armed forces and to take those exceptional measures to ensure that we have in fact taken all feasible measures to ensure that a 17 year old does not take direct participation in hostilities; exactly as is required under the optional protocol. 
United States, Statement by the Deputy Assistant Secretary, Detainee Affairs, Department of Defense, at a press briefing with the Ambassador-at-Large and Director, Office to Monitor and Combat Trafficking in Persons, Geneva, 21 May 2008.