Related Rule
United States of America
Practice Relating to Rule 100. Fair Trial Guarantees
Section H. Assistance of an interpreter
The US Field Manual (1956) reproduces Articles 96 and 105 of the 1949 Geneva Convention III. 
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, §§ 172 and 181.
The manual also uses the same wording as Articles 72 and 123 of the 1949 Geneva Convention IV. 
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, §§ 442 and 330.
The US Air Force Pamphlet (1976) provides that Article 105 of the 1949 Geneva Convention III “gives [the prisoner of war] the right to … the services of a competent interpreter”. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 13-8.
The Pamphlet also states: “Among other rights, accused persons are assured the right to … obtain an interpreter”. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 14-6.
The US Air Force Commander’s Handbook (1980) states that prisoners must be allowed “the help of … an interpreter” in case of trial. 
United States, Air Force Pamphlet 110-34, Commander’s Handbook on the Law of Armed Conflict, Judge Advocate General, US Department of the Air Force, 25 July 1980, § 4-2(c).
The US Naval Handbook (1995) states: “At a minimum, [procedural] rights must include the assistance of … an interpreter”. 
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), § 11.7.1.
The US Manual for Military Commissions (2007) states:
Interpreters. The convening authority may detail or employ for the military commission interpreters who shall interpret for the commission and as necessary, for the trial counsel, defense counsel, and the accused. 
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 501(d), p. II-19.
The US Naval Handbook (2007) states:
Prisoners of war prosecuted for war crimes committed prior to capture, or for serious offenses committed after capture, are entitled to be tried by the courts that try the captor’s own forces and are to be accorded the same procedural rights. At a minimum, these rights must include the assistance of … an interpreter. 
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, § 11.3.1.1.
The US Manual for Military Commissions (2010) states:
Composition and personnel of military commission
(d) Interpreters. The convening authority may detail or employ for the military commission interpreters. 
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 501(d), p. II-22.
The manual also states:
Qualifications and duties of personnel of military commissions
(e) Interpreters, reporters, escorts, bailiffs, clerks, and guards.
(3) Duties
(A) Interpreters. Interpreters shall interpret for the commission and as necessary, for the trial counsel and defense counsel and for the accused. 
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 502(e)(3)(A), p. II-28.
The US Regulation for Trial by Military Commissions (2007), designed to facilitate the day-to-day functioning of US Military Commissions by implementing the provisions of the Military Commissions Act of 2006 (MCA) and the Manual for Military Commissions (MMC), states:
In each case before a military commission and in each instance of the taking of a deposition, the convening authority or the officer directing such proceeding shall appoint, when necessary, an interpreter for the commission or officer taking the deposition. 
United States, Regulation for Trial by Military Commissions, 27 April 2007, § 7-3.a, p. 30.
The US Military Commissions Act (2009) amends Chapter 47A of Title 10 of the United States Code as follows:
§ 948l. Detail or employment of reporters and interpreters
“ …
“(b) INTERPRETERS.—Under such regulations as the Secretary of Defense may prescribe, the convening authority of a military commission under this chapter may detail to or employ for the military commission interpreters who shall interpret for the military commission, and, as necessary, for trial counsel and defense counsel for the military commission, and for the accused. 
United States, Military Commissions Act, 2009, § 948l(b).