Efforts to regulate warfare, including the use of particular weapons, have a long history, dating back, according to some scholars, thousands of years. But international codification of the rules of war in binding multilateral legal instruments only began in the second half of the nineteenth century. Among the first such efforts was one devoted to the prohibition of the use of a particular weapon in wartime. The St. Petersburg Declaration of 1868 on exploding bullets banned the use of explosive projectiles under 400 grammes in weight and is generally recognised as constituting the first significant international instrument prohibiting a specific weapon. It also incorporated into the conventional law of armed conflict the customary principle prohibiting the use of weapons ‘of a nature to cause superfluous injury or unnecessary suffering’ — a tenet of international humanitarian law and a touchstone for many important international agreements on the use of weapons that have since followed, including the Hague Declaration of 1899 on expanding bullets, the Geneva Gas Protocol of 1925 and, most recently, the United Nations Convention on Conventional Weapons of 1980 (hereafter, CCW).
