Related Rule
United States of America
Practice Relating to Rule 91. Corporal Punishment
The US Field Manual (1956) forbids corporal punishment of prisoners of war and civilians. 
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, §§ 163 and 271.
The US Manual on Detainee Operations (2008) states that “imposition of physical punishment is inconsistent with the humane treatment obligation”. 
United States, Manual on Detainee Operations, Joint Chiefs of Staff, 30 May 2008, p. III-10.
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:
“SUBCHAPTER V—SENTENCES
§ 949s. Cruel or unusual punishments prohibited
“Punishment by flogging, or by branding, marking, or tattooing on the body, or any other cruel or unusual punishment, may not be adjudged by a military commission under this chapter or inflicted under this chapter upon any person subject to this chapter. The use of irons, single or double, except for the purpose of safe custody, is prohibited under this chapter. 
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. 2617, § 949s.
The US Military Commissions Act (2009) amends Chapter 47A of Title 10 of the United States Code as follows:
§ 949s. Cruel or unusual punishments prohibited
“Punishment by flogging, or by branding, marking, or tattooing on the body, or any other cruel or unusual punishment, may not be adjudged by a military commission under this chapter or inflicted under this chapter upon any person subject to this chapter. The use of irons, single or double, except for the purpose of safe custody, is prohibited under this chapter. 
United States, Military Commissions Act, 2009, § 949s.
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.