Rule 74. The use of chemical weapons is prohibited.

Practice

Volume II, Chapter 24, Section A.

Summary

State practice establishes this rule as a norm of customary international law applicable in both international and non-international armed conflicts.

International armed conflicts

The use of chemical weapons is prohibited in international armed conflicts in a series of treaties, including the Hague Declaration concerning Asphyxiating Gases, the Geneva Gas Protocol, the Chemical Weapons Convention and the Statute of the International Criminal Court. At present, only 13 States are not party to either the Geneva Gas Protocol or the Chemical Weapons Convention. Of these, at least three have made statements to the effect that the use of chemical weapons is unlawful, or have indicated that they do not possess or use them or that they are committed to their elimination. The prohibition is also contained in a number of other instruments.

Numerous military manuals restate the prohibition of the use of chemical weapons. This prohibition is also contained in the legislation of many States. There are numerous statements and other practice by States from all parts of the world to the effect that the use of chemical weapons is prohibited under customary international law. Most allegations of use since the 1930s either are unsubstantiated or have been denied; the few confirmed cases have been widely denounced by other States. There is also national case-law to the effect that the use of chemical weapons is prohibited under customary international law.