By James A. Schoettler, Jr
Customary international law (CIL) is an important source of legally binding rules applicable in armed conflict. Where a party to a conflict has not ratified a key international humanitarian law (IHL) treaty, such as the 1977 Protocol (I) Additional to the Geneva Conventions of 12 Aug. 1949, Relating to the Protection of Victims of International Armed Conflicts (AP I), that party may need to turn to CIL to determine the applicable rules. Further, even where all parties have ratified key treaties, CIL may fill in gaps not explicitly addressed in the treaties.
The U.S. Department of Defense (DoD) Law of War Manual includes a number of references to existing CIL. Generally, these references reiterate longstanding U.S. government positions on what is and is not CIL. However, in the July 2023 revision of the Manual, the drafters stated that a newly-revised provision of the Manual, which adopted certain presumptions applicable when there is doubt whether a person or object is targetable, reflects CIL in the view of the DoD. This statement is remarkable considering the longstanding position of the United States that these presumptions do not reflect CIL.
