Related Rule
United States of America
Practice Relating to Rule 88. Non-Discrimination
Section D. Persons deprived of their liberty
The US Field Manual (1956) provides: “All POWs [prisoners of war] shall be treated alike without any adverse distinction based on race, nationality, religious belief or political opinions, or any other distinction founded on similar criteria.” 
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, § 92.
The US Air Force Pamphlet (1976) prohibits any adverse distinction with regard to prisoners of war. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, §§ 12–2(a) and 13-2.
The US Naval Handbook (1995) provides: “When prisoners of war are given medical treatment, no distinction among them will be based on any grounds other than medical ones.” 
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.
The US Naval Handbook (2007) states: “Humane treatment is … [to] be afforded to all detained persons without adverse distinction based on race, color, religion or faith, sex, birth or wealth, or any other similar criteria”. 
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, § 11.2.
The Handbook also states: “When prisoners of war are given medical treatment, no distinction among them will be based on any grounds other than medical ones.” 
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(6); see also § 11.3.1.
The US Manual on Detainee Operations (2008) states:
DODD 2310.01E [Department of Defense Directive, The Department of Defense Detainee Program] requires that all DOD [Department of Defense] personnel and contractors will apply, without regard to a detainee’s legal status, at a minimum, the standards articulated in Common Article 3 to the Geneva Conventions of 1949 …
Article 3 Common to the Geneva Conventions of 1949
In the case of armed conflict not of an international character occurring in the territory of one of the High Contracting Parties, each Party to the conflict shall be bound to apply, as a minimum, the following provisions:
(1) Persons taking no active part in the hostilities … shall in all circumstances be treated humanely, without any adverse distinction founded on race, colour, religion or faith, sex, birth or wealth, or any other similar criteria. 
United States, Manual on Detainee Operations, Joint Chiefs of Staff, 30 May 2008, pp. III-11–III-12.
The manual also states:
The detaining power is … prohibited from imposing any adverse distinctions within the detainee population based on religion. In this regard, it should be noted that in some situations, segregating the detainee population based on religious affiliation may be beneficial and therefore not prohibited, particularly when conflict has been based in part on religious affiliation. 
United States, Manual on Detainee Operations, Joint Chiefs of Staff, 30 May 2008, pp. III-8.