Related Rule
United States of America
Practice Relating to Rule 49. War Booty
The US Field Manual (1956), in a paragraph entitled “Booty of war”, provides:
All enemy public movable property captured or found on a battlefield becomes the property of the capturing State … Enemy private movable property, other than arms, military papers, horses, and the like captured or found on a battlefield, may be appropriated only to the extent that such taking is permissible in occupied areas. 
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, § 59(a) and (b); see also § 396.
Concerning the property of prisoners, the manual specifies:
All effects and articles of personal use, except arms, horses, military equipment and military documents, shall remain in the possession of prisoners of war, likewise their metal helmets and gas masks and like articles issued for personal protection. Effects and articles used for their clothing or feeding shall likewise remain in their possession, even if such effects and articles belong to their regular military equipment. 
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, § 94; see also § 59(c).
The US Soldier’s Manual (1984) states:
After you have secured, silenced, and segregated captives, you may search them for items of military or intelligence value only, such as weapons, maps, or military documents. Do not take protective items, such as gas masks, mosquito nets, or parkas; or personal items of no military value such as jewelry, photos, or medals from captured or detained personnel. 
United States, Your Conduct in Combat under the Law of War, Publication No. FM 27-2, Headquarters Department of the Army, Washington, November 1984, p. 19.
The US Instructor’s Guide (1985) provides:
[Prisoners of war] are entitled to retain most of [their] personal property. The conventions provide that all effects and articles of personal use, except arms, military equipment, and military documents, must remain in the possession of the prisoner unless he could use them to harm himself or others. Articles issued for the prisoner’s personal protection, such as gas masks and metal helmets, may also be retained by him. 
United States, Instructor’s Guide – The Law of War, Headquarters Department of the Army, Washington, April 1985, p. 11.
The US Rules of Engagement for Operation Desert Storm (1991) states: “The taking of war trophies [is] prohibited.” 
United States, Desert Storm – Rules of Engagement, Pocket Card, US Central Command, January 1991, reprinted in Operational Law Handbook, International and Operational Law Department, The Judge Advocate General’s School, United States Army, Charlottesville, Virginia, 1995, pp. 8-7 and 8-8, Point F.
In the Morrison case in 1974, the US Court of Claims denied a claim of a former soldier who had discovered $50,000 in an area abandoned by the enemy. The Court held that the soldier had taken possession of the money solely as an agent of the United States and had no legal basis to claim its return. 
United States, Court of Claims, Morrison case, Judgment, 20 February 1974.