Related Rule
United States of America
Practice Relating to Rule 116. Accounting for the Dead
Section C. Marking of graves and access to gravesites
The US Field Manual (1956) provides that the graves of the dead are “marked so that they may always be found”. 
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, § 218.
The Annotated Supplement to the US Naval Handbook (1997) requires that “as soon as circumstances permit, arrangement be made to facilitate access to grave sites by relatives”. 
United States, Annotated Supplement to the Commander’s Handbook on the Law of Naval Operations, prepared by the Oceans Law and Policy Department, Center for Naval Warfare Studies, Naval War College, Newport, Rhode Island, November 1997, § 11.4, footnote 19.
In 1987, the Deputy Legal Adviser of the US Department of State affirmed: “We support … the principle that … the remains of the dead be … marked … [and] as soon as circumstances permit, arrangements be made to facilitate access to grave sites by relatives.” 
United States, Remarks of Michael J. Matheson, Deputy Legal Adviser, US Department of State, The Sixth Annual American Red Cross-Washington College of Law Conference on International Humanitarian Law: A Workshop on Customary International Law and the 1977 Protocols Additional to the 1949 Geneva Conventions, American University Journal of International Law and Policy, Vol. 2, 1987, p. 424.