The United States has historically led the international community in establishing regimes intended to limit the spread of nuclear, chemical, and biological weapons and missiles. The regimes and their member countries use cooperative and coercive measures to achieve nonproliferation and counterproliferation objectives. Multilateral agreements and organizations are supplemented by strong bilateral cooperation among key allies, unilateral political and economic actions, and recourse to military operations should they become necessary. Congress supports the nonproliferation regimes primarily by providing statutory authority and funding for U.S. participation, establishing policy, and mandating punitive actions to help enforce the international standards set by the regimes. The term "regime" often refers to the entire array of international agreements, multilateral organizations, national laws, regulations, and policies to prevent the spread of dangerous weapons and technologies. The nuclear nonproliferation regime is presently the most extensive, followed by those dealing with chemical and biological weapons, and then by the missile regime. The difficulty of producing nuclear weapons material (highly enriched uranium or plutonium) and the great awareness of nuclear weapons' destructiveness together have been conducive to creating a complex regime with widespread agreement on the priority of nuclear nonproliferation. Chemical weapons are easier to make and rely on readily available precursors, and they are far less destructive. Biological weapons also rely on dual-use technology, and as technology has spread, efforts to build a more extensive control regime have intensified. Finally, there is no international consensus on the danger of missile proliferation to support a nonproliferation treaty or a binding regime with enforcement mechanisms. A key aspect of all the regimes is their attempt to control exports of sensitive goods and technologies through supplier agreements. These are the Nuclear Suppliers Group and the Zangger Committee for nuclear technology, the Australia Group for chemical and biological weapons technology, and the Missile Technology Control Regime. In the last decade, these export control regimes have expanded their membership, expanded and refined their control lists, and increased coordination among member states. At the same time, however, the non-binding nature of some of the regimes and growing resistance to them by certain countries, including some regime members, limits their effectiveness. A major dilemma is whether to include new members, that may not be U.S. allies and may not have reliable export controls, or to limit membership to countries with excellent nonproliferation credentials. Regime members may be afforded special access to controlled technology by the other members, so this issue also affects decisions on whether to include non-allies. Table 1 lists the proliferation control regimes, their components and statutory authority. There are many arms control treaties and other activities that address aspects of WMD and conventional weapons beyond the regimes covered in this report. Although proliferation control regimes are a useful tool in preventing dangerous technology transfers, several factors undermine their effectiveness. One is the difficulty of addressing underlying motivations of countries to acquire weapons of mass destruction (WMD). Regional security conditions as well as the desire to compensate for other countries' superior conventional or unconventional forces have been common motivations for WMD programs. Some countries may want WMD to dominate their adversaries. Prestige is another reason why certain countries seek WMD. Another factor working against the regimes is the steady diffusion of technology over time—much of the most significant WMD technology is 50 years old, and growing access to dual-use equipment makes it easier for countries or groups to build their own WMD production facilities from commonly available civilian equipment. There are at least two problems common to all of the nonproliferation regimes—the lack of universal membership and gaps in verification. In the nuclear regime, India, Pakistan, North Korea, and Israel are not members of the NPT. Apart from diplomatic questions about how to treat their status as states with nuclear weapons not sanctioned by the NPT, those countries are not bound by that treaty's prohibition on sharing nuclear technology, nor are they committed to eventually eliminating these weapons. They are also not members of the export control groups. The international community struggles with how to bring these states into the nonproliferation regimes without tacitly agreeing to their acquisition of nuclear weapons. For example, a major objection to the U.S. nuclear cooperation agreement with India was the perception that it legitimizes India's nuclear weapons program without extracting any significant concessions on limiting its nuclear arsenal. Like India, Pakistan is not bound by any NPT obligations, whether or not Pakistani scientist A.Q. Khan sold nuclear technology on the black market with or without Pakistani government acquiescence. Revelations in 2004 of centrifuge enrichment technology sales to Libya, Iran, and North Korea galvanized the international community to examine strengthening implementation of national export controls and interdiction. In the chemical and biological weapons (CBW) area, some states suspected of having military programs are still outside the treaty. Within the treaties, there are some members (e.g., Iran under the CWC and Russia under the BWC) suspected of continuing programs. In the missile area, although the Hague Code of Conduct has widespread membership, MTCR is still not adhered to by many states (e.g., China, North Korea) that are responsible for proliferating missile technologies. Continued diplomatic support for the treaties and export control regimes may face some hurdles. In the nuclear nonproliferation regime, many non-weapons states link their continued cooperation with progress in implementing Article VI of the treaty (steps toward eventual nuclear disarmament by the five nuclear weapons states). Some non-nuclear-weapon states are also resistant to accepting any limitations on nuclear technology exports involving advanced fuel production technology that has the potential to produce weapons grade material. These states view such restrictions as limiting their access to peaceful nuclear technology as guaranteed by the NPT. Thus, as dual-use equipment in all WMD fields becomes more widespread, there may be a higher expectation that exporters will need to better control where their technology goes and how it is used. In addition to a formal framework of control agreements, close political relationships with key allies and other countries are very important for U.S. efforts to counter the spread and the use of WMD. Initiatives by allies, such as the G-8 Global Partnership to Combat the Spread of WMD, demonstrate resolve to tackle specific proliferation problems. In May 2003, President Bush launched the " Proliferation Security Initiative ." President Obama hosted the first Nuclear Security Summit in 2010. Many of these relationships, nonetheless, are strongly influenced by other political, military, and economic issues that sometimes take precedence over proliferation concerns. In practice, nonproliferation competes with important policy objectives such as trade, regional issues, and domestic political considerations, and uneven implementation of nonproliferation policy can result. A more difficult challenge exists when U.S. allies and friends seek WMD and missiles of their own or transfer WMD technology. Perhaps the hardest challenge for nonproliferation policies is to reduce the desire of countries for weapons of mass destruction. It is sometimes possible to change regional security conditions through alliances, conventional arms transfers, arms control, or negotiations aimed at settling conflicts. However, eliminating underlying motivations takes time, and the next best option may be to delay WMD development for as long as possible, or to attempt to impact a country's calculation of the costs of pursuing these weapons. Libya's decision in December 2003 to give up its nuclear, chemical weapons, and missile programs is a good example of a state that apparently decided the costs of WMD programs exceeded their benefits. Unilaterally, the United States uses sanctions to support its nonproliferation objectives. Various laws authorize or require the President to impose unilateral sanctions on countries that acquire, use, or help other countries to obtain WMD or missiles. Sanctions can affect U.S. aid, cooperation, and impose restrictions on U.S. technology exports. The effectiveness of sanctions often depends on persuading other countries to support or respect U.S. sanctions. Even without multilateral support, sanctions can still highlight strong U.S. opposition to WMD proliferation. However, strong sanctions are rarely imposed on U.S. friends or allies that acquire WMD. U.S. armed forces have developed programs to help prevent the spread of WMD, to deter or prevent their use, and to protect against their effects. Defense cooperation and arms transfers to U.S. allies can ease concerns about security that can lead them to consider acquiring WMD, and also signal potential adversaries that acquisition or use of WMD may evoke a strong military response. U.S. conventional and nuclear military capabilities and the threat of retaliation help deter WMD attacks against U.S. forces, territory, or allies. Counterproliferation capabilities have been expanded in recent years to include more advanced "passive" and "active" defense measures. Passive counterproliferation tools include protective gear such as gas masks and detectors to warn of the presence of WMD. Active measures include missile defenses to protect U.S. territory, forces, and allies; precision-guided penetrating munitions and special operation forces to attack WMD installations; and intelligence gathering and processing capabilities. Intelligence is crucial to U.S. nonproliferation efforts, particularly in helping shape policy options. Intelligence agencies track foreign WMD programs, monitor treaty compliance, and attempt to detect transfers of WMD goods and technology. The United States cooperates with certain allies to prepare for possible counterproliferation actions. Although counterproliferation is a main pillar of U.S. strategy to combat WMD, political and technical hurdles (hidden underground bunkers, locations near civilians, etc.) tend to make counterproliferation a last resort, after other options have failed. One key tool of counterproliferation has been interdiction of WMD-related equipment shipments at sea, on land, and by air.