Related Rule
Ukraine
Practice Relating to Rule 117. Accounting for Missing Persons
Section D. Right of the families to know the fate of their relatives
Ukraine’s IHL Manual (2004) states:
“Missing persons” mean persons who are missing during hostilities and whose whereabouts are unknown.
Regarding such persons, the Parties to an armed conflict shall be primarily guided by the right of the families to know about the fate of their relatives. 
Ukraine, Manual on the Application of IHL Rules, Ministry of Defence, 11 September 2004, § 1.2.29.