White phosphorus munitions produce fire when their chemical contents react with oxygen. Due to their incendiary effects, these munitions cause painful and penetrating burns as well as respiratory damage and organ failure. Individuals who survive initial exposure experience long-term physical, psychological, and socioeconomic harm. The use of airburst white phosphorus munitions over populated areas, such as Israel’s attacks in southern Lebanon from 2023-2026, is indiscriminate and violates international humanitarian law, also known as the laws of war. The impacts of white phosphorus munitions have been described by states and a range of experts as cruel, excruciating, horrific, and unacceptable.

White phosphorus munitions, however, fall within a legal gap because they are not covered by specific international law. The 1980 Protocol III to the Convention on Conventional Weapons (CCW) regulates incendiary weapons, which it defines as being “primarily designed” to set fires and burn people. This definition excludes weapons that are designed for other purposes even if they produce the same incendiary effects. It does not encompass white phosphorus munitions—generally designed to be used as obscurants or illuminants—although their humanitarian consequences are comparable to those of weapons defined by the protocol as incendiary.

This report assesses white phosphorus munitions as exemplars of so-called “weapons with incendiary effects” under the Martens Clause. The clause dates back to the 1899 Hague Convention and has since appeared in international humanitarian and disarmament law treaties, including Additional Protocol I to the 1949 Geneva Conventions, adopted in 1977, and the CCW.

The Martens Clause is triggered when there is no treaty dedicated to a topic, as is the case with white phosphorus munitions. The clause sets out that in such cases, established custom, the principles of humanity, and the dictates of public conscience provide protection for civilians and combatants. This report finds that white phosphorus munitions violate both the principles of humanity and dictates of public conscience. Stronger and more specific law is, therefore, needed to bolster humanitarian protections from munitions containing white phosphorus.

The Martens Clause provides an appropriate framework for examining white phosphorus munitions given the clause’s role in the history of the CCW and its protocols. Concerns about the principles of humanity and dictates of public conscience helped motivate the drafters of Protocol III on incendiary weapons; these concerns are equally applicable to white phosphorus munitions. In addition, the CCW’s preamble includes the Martens Clause, suggesting that it is a fitting rationale for future regulation.

Report by the Human Rights Watch