This chapter provides an overview of treaty and customary international law rules applicable to means of combat. Belligerents do not need an authorization from international humanitarian law in relation to a specific means of combat. Rather, they are free to develop, produce, stockpile, transfer, or use any particular weapon, except for those cases in which a prohibitive rule of international humanitarian law dictates to the contrary. In order to guarantee effective implementation of the prohibition of certain means and methods of warfare, it is necessary to provide for an efficient procedure to ensure the legality of new weapons. This procedure is preventive in nature and aims at providing the belligerents with means of combat that do not violate international law prohibitions. The chapter discusses the prohibition of certain conventional weapons and then looks at weapons of mass destruction, which are simply defined as nuclear, chemical, and biological weapons. While the production, possession, and use of chemical weapons and biological weapons is prohibited under treaty law, the legal status of nuclear weapons is more complex.
