Under Article 36 of the 1977 Additional Protocol I to the Geneva Conventions, States are required to review new weapons for their compliance with international law. While recent discussions on the regulation of lethal autonomous weapons systems under the auspices of the UN Certain Conventional Weapons Convention increasingly emphasize the importance of national weapons review mechanisms, Article 36 is known to be implemented only by a handful of States. Some legal scholars have nonetheless argued that the Article 36 obligation has attained customary international law status. Remarkably, substantive analysis of State practice and opinio juris required to evidence that certain conduct of States has advanced to a level of customary international law is absent in these claims.
This article examines whether the weapons review obligation as formulated under Article 36 is mandated by customary international law. An affirmative answer to this question would require evidence of “extensive and virtually uniform” State practice showing that new weapons are legally reviewed at the earliest stage in the acquisition process as a matter of law. The article concludes that no such evidence exists. It then considers “alternate” weapons reviews by asking whether a narrower obligation to review weapons before fielding forms part of customary international law. It finds that the existence of such a rule is also unsupported by State practice and opinio juris.