All States are required to ensure that their use of weapons in armed conflict is consistent with their international law obligations. There are two sources of the legal review obligation: firstly the express obligation upon States party to the Additional Protocol I by virtue of Article 36; and, secondly, an indirect obligation of the good faith to comply with the object and purpose of a State’s treaty obligations. It is important for States to understand the source of their legal review obligation as it defines the scope and content.
The origin of both legal review obligations can be traced to the 1868 St. Petersburg Declaration. In particular, while not creating an express obligation to review weapons, the drafters clearly contemplated the need for States to consider the legality of future weapons. This is evident from the last paragraph of the 1868 St. Petersburg Declaration which states that:
‘The Contracting or Acceding Parties reserve to themselves to come hereafter to an understanding whenever a precise proposition shall be drawn up in view of future improvements which science may effect in the armament of troops, in order to maintain the principles which they have established, and to conciliate the necessities of war with the laws of humanity.’
The Hague Peace Conferences, building upon the sentiment of the St. Petersburg Declaration, strengthened the emerging realisation that the use of weapons must be internationally regulated by codifying laws prohibiting certain weapons and weapon effects. The obligation was reinforced by Article 1 of the 1899 Hague Declaration II with Respect to the Laws and Customs of War as it requires States Party to issue instructions to their armed forces that conform to the rules contained in Annex A to the Convention. It is unlikely that Article 1 requires the conduct of weapon reviews however W. Hays Parks argues that this obligation, read in light of rules such as Article 23(e) prohibiting the employment of ‘arms, projectiles or material of a nature to cause superfluous injury’ obligates State to ensure the legality of weapons. This article was re-adopted, without substantive amendment, in the equivalent articles of the 1907 Hague Convention IV which is recognized by the International Military Tribunal at Nuremburg and, more recently, the International Court of Justice as declarative of customary international law.
However, it wasn’t until the drafting of the Additional Protocol I that an express weapon review obligation was created. Prior to this time, States were subject to an indirect obligation to ensure that their possession and use of weapons were consistent with their international legal obligations. As a consequence, very few States undertook a formal legal review process.