Related Rule
United States of America
Practice Relating to Rule 126. Visits to Persons Deprived of Their Liberty
The US Field Manual (1956) reproduces Article 116 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, § 323.
The US Manual on Detainee Operations (2008) states: “[P]rograms [for detainees] that may be considered, where feasible and consistent with security limitations and/or mission accomplishment, include establishment of a family visitation program.” 
United States, Manual on Detainee Operations, Joint Chiefs of Staff, 30 May 2008, p. III-9.
In a chapter on “Roles and Responsibilities”, the manual states:
Commander, Detainee Operations
… The CDO will have the following responsibilities:
… Obtain theater commander’s approval for external visit times and coordinate visits to detainee facilities with the TDRC [theater detainee reporting center] and joint visitor bureau. 
United States, Manual on Detainee Operations, Joint Chiefs of Staff, 30 May 2008, pp. II-3–II-4.
The manual also states:
Detainee Categories
The DOD [Department of Defense] definition of the word “detainee” includes any person captured, detained, or otherwise under the control of DOD personnel (military, civilian, or contractor employee) … It does not include persons being held primarily for law enforcement purposes except where the United States is the occupying power …
a. Enemy Combatant. In general, a person engaged in hostilities against the United States or its coalition partners during an armed conflict. The term “enemy combatant” includes both “lawful enemy combatants” and “unlawful enemy combatants.”
b. Enemy Prisoner of War. Individual under the custody and/or control of the DOD according to Articles 4 and 5 of the … [1949 Geneva Convention III].
c. Retained Personnel … Personnel who fall into the following categories: official medical personnel of the armed forces exclusively engaged in the search for, or the collection, transport, or treatment of wounded or sick, or in the prevention of disease, and staff exclusively engaged in the administration of medical units and facilities; chaplains attached to enemy armed forces; staff of national Red Cross Societies and that of other volunteer aid societies duly recognized and authorized by their governments to assist medical service personnel of their own armed forces, provided they are exclusively engaged in the search for, or the collection, transport or treatment of, the wounded or sick, or in the prevention of disease, and provided that the staff of such societies are subject to military laws and regulations.
d. Civilian Internee … A civilian who is interned during an armed conflict, occupation, or other military operation for security reasons, for protection, or because he or she has committed an offense against the detaining power. 
United States, Manual on Detainee Operations, Joint Chiefs of Staff, 30 May 2008, pp. I-3–I-5; see also pp. viii and GL-3.