Related Rule
United States of America
Practice Relating to Rule 128. Release and Return of Persons Deprived of Their Liberty
Section D. Voluntary nature of return
The US Field Manual (1956) provides: “No sick or injured prisoner of war who is eligible for repatriation may be repatriated against his will during hostilities.” 
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, § 188.
The US Air Force Pamphlet (1976) provides: “No wounded and sick PW [prisoner of war] eligible for repatriation may be repatriated against his will during hostilities.” 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 13-10.