Article 36 of Additional Protocol I of 1977 states that:
“In the study, development, acquisition or adoption of a new weapon, means or method of warfare, a High Contracting Party is under an obligation to determine whether its employment would, in some or all circumstances, be prohibited by this Protocol or by any other rule of international law applicable to the High Contracting Party”.
The provision is not new law, but codifies the customary law duty of implementing a treaty or customary rule in good faith. Article 36 does, however, draw attention to the fact that new developments in weapons are quietly going on, and that care must be taken, before their deployment, that their use in some or all circumstances does not violate international humanitarian law. Although the duty to determine in advance the legality of the use of new weapons lies with the State developing them, other States have a legal interest in ensuring that this is done.