Weapons of Mass Destruction and International Law
By David P. Fidler
The perceived threat from weapons of mass destruction (WMD) has become one of the most important issues on foreign policy and national security agendas. The WMD threat has, for example, profoundly influenced the Bush administration's national security and homeland security strategies.  For the United States and like-minded allies, Iraq's alleged possession of WMD has become a casus belli. The rise to prominence of the WMD threat raises questions about the role of international law concerning WMD in this new environment.
Traditional International Legal Approaches to WMD
In security and foreign policy analyses, "weapons of mass destruction" is a term that generally encompasses nuclear, chemical, and biological weapons, with radiological weapons occasionally included. Contemporary international legal analysis generally follows this conventional definition of WMD, even though neither treaty law nor customary international law contains an authoritative definition of WMD. The reason such a definition does not exist is that states have historically used international law to address each category of weapons within the WMD rubric. International law specifically on WMD is, thus, composed of three different sets of rules for each WMD technology. General rules of international law, such as international humanitarian law, also apply to WMD;  but these general principles were not developed specifically to address WMD.
The dominant international legal activity on WMD has been the negotiation and implementation of arms control treaties. This arms control approach reflected three objectives-to deter the use of WMD by states (e.g., nuclear arms control treaties between the United States and the Soviet Union  ), to prohibit the emplacement and testing of WMD in certain areas (e.g., treaties prohibiting WMD in orbit or on the sea-bed or ocean floor  ), and to produce WMD disarmament (e.g., treaties prohibiting development and use of biological and chemical weapons  ). Although arms control treaties contributed to the development of customary norms restricting or prohibiting the use of WMD, development and possession of WMD was not, outside the treaty context, illegal under customary international law.
The Transformation of the WMD Policy and Legal Environment
In the post-Cold War period, political and technological developments created three WMD challenges that rendered the historical reliance on arms control treaties suspect. First, in the 1990s, concern mounted about WMD proliferation by states and terrorist groups, suggesting the world confronted increasing interest in WMD by state and non-state actors. In light of these increasing motivations to possess WMD, the traditional arms control approach seemed insufficient to address either kind of proliferation.
Second, experts argued that the technological difficulties traditionally confronted in developing WMD were diminishing for state and non-state actors. Advances in biotechnology and genetic engineering revolutionized, for example, the technological context of bioweapons. The arms control approach had long struggled with the challenges posed by the dual-use nature of all WMD technologies; and the transformed technological contexts exacerbated the dual-use problem and complicated verification efforts in arms control for all three WMD areas. The perceived increase in the technological feasibility of WMD development combined with concerns about growing state and terrorist interest in WMD to compound fears about the WMD threat.
Third, the political and technological developments described above forced governments to confront the vulnerabilities their societies faced from terrorism involving WMD. Events, such as the chemical terrorism perpetrated by Aum Shinriyko in Japan in 1995, stimulated efforts to improve domestic preparedness for catastrophic terrorism. The September 11th and anthrax attacks accelerated attempts in the United States and other countries to improve "homeland security." The arms control approach to WMD did not address the vulnerability crises countries faced in the post-Cold War period.
International Law in the New WMD Environment
The transformation of the WMD policy and legal environment has produced awareness that the arms control approach does not adequately address the political, technological, and preparedness challenges countries now confront with WMD. Although arms control remains important, the new WMD environment is witnessing a diversification in how states and international organizations use international law in connection with the WMD threat.
In connection with the perceived increase in WMD proliferation by states and non-state actors, new international legal efforts and proposals aimed at strengthening deterrence against WMD development and use have appeared. These include: (1) Security Council action against Iraq concerning its alleged WMD programs;  (2) U.S. efforts to extend the right of anticipatory self-defense to justify military action in "pre-emptive self-defense" against a hostile regime armed with or pursuing WMD;  (3) criminalizing WMD terrorism in treaty law;  and (4) proposals to make the development, retention, acquisition, or transfer of biological and chemical weapons a crime under international law. 
International cooperation and legal activity has also begun to address the increasing technological feasibility of WMD. International efforts to improve national control and regulation of access to, and transfer of, WMD materials have started, for example, within the Australia Group and through the Biological Weapons Convention. Multilateral initiatives, such as the G-8 Global Partnership Against the Spread of Weapons and Materials of Mass Destruction,  also contribute to international activities designed to protect WMD materials from malevolent appropriation. In the same spirit, experts have proposed new treaties on improving the safety and security of biological agents. 
The challenge of domestic preparedness is also the subject of international diplomatic and legal activities. Strengthening domestic preparedness against WMD terrorism has become, for example, an agenda item in a number of multilateral forums, including NATO, the World Health Organization, World Customs Organization, and the International Maritime Organization. In addition, specific multilateral initiatives, such as the Ottawa Plan,  have made improved domestic preparedness for WMD terrorism the focus of diplomatic attention.
In the new WMD environment, states and international organizations are diversifying the role international law plays in connection with the WMD threat. The traditional arms control approach no longer monopolizes the international legal strategy against WMD. This development suggests that the need for international law in connection with the WMD threat may be higher now than in previous historical periods. The dangers and uncertainties confronting the use of international law in this new WMD environment may also be historically unprecedented, as U.S. interpretations of international law to justify military action against Iraq and the worsening crisis with North Korea both demonstrate.
For further discussion of related issues, please see the previous ASIL Insights, North Korea's Withdrawal from the Nuclear Nonproliferation Treaty, Security Council Resolution 1441 on Iraq's Final Opportunity to Comply with Disarmament Obligations, and Pre-emptive Action to Forestall Terrorism.
 See, e.g., The National Security Strategy of the United States of America (Sept. 2002), http://www.whitehouse.gov/nsc/nss.html and National Strategy for Homeland Security (July 2002), http://www.whitehouse.gov/homeland/book/index.html.
 See, e.g., Advisory Opinion, Legality of the Use of Force by a State of Nuclear Weapons in Armed Conflict, ICJ Reports 66 (1996), http://www.icj-cij.org/icjwww/icases/iunan/iunanframe.htm.
 See, e.g., Treaty Between the United States of American and the Union of Soviet Socialist Republics on the Limitation of Anti-Ballistic Missile Systems, Oct. 3, 1972, at http://www.state.gov/t/np/trty/16332.htm.
 See, e.g., Treaty on Principles Governing the Activities of States in the Exploration of Outer Space, Including the Moon and Other Celestial Bodies, January 27, 1967, at http://www.state.gov/t/ac/trt/5181.htm; and Treaty on the Prohibition of the Emplacement of Nuclear Weapons and Other Weapons of Mass Destruction on the Sea-Bed and the Ocean Floor and in the Subsoil Thereof, Feb. 11, 1971, at http://www.state.gov/t/ac/trt/5187.htm.
 See Convention on the Prohibition of the Development, Production and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on Their Destruction, Apr. 10, 1972, at http://www.state.gov/t/ac/trt/4718.htm; and Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on Their Destruction, Jan. 13, 1993, at http://www.state.gov/t/np/trty/16286.htm.
 National Security Strategy of the United States, supra note 1, at 15; National Strategy to Combat Weapons of Mass Destruction (Dec. 2002), http://www.whitehouse.gov/news/releases/2002/12/WMDStrategy.pdf.
 U.N. Convention on the Suppression of Terrorist Bombings, Jan. 12, 1998, Art. 1.3(b), at http://untreaty.un.org/English/Terrorism/Conv11.pdf.
 Harvard/Sussex Program on CBW Disarmament and Arms Limitation, Draft Convention on the Prevention and Punishment of the Crime of Developing, Producing, Acquiring, Stockpiling, Retaining, Transferring, or Using Biological or Chemical Weapons, http://fas-www.harvard.edu/~hsp/crim01.pdf.
 See, e.g., Jonathan B. Tucker and Raymond A. Zilinskas, Assessing U.S. Proposals to Strengthen the Biological Weapons Convention, Arms Control Today (Apr. 2002), http://armscontrol.org/act/2002_4/tuzilapril02.asp.
The purpose of ASIL Insights is to provide concise and informed background for developments of interest to the international community. The American Society of International Law does not take positions on substantive issues, including the ones discussed in this Insight.