This dissertation argues that the Nunn-Lugar Cooperative Threat Reduction (CTR) program, which is designed to curb nuclear proliferation, has become a security regime. Since the end of the Cold War, the Nunn-Lugar CTR program has dismantled nuclear, chemical and biological weapons in the former Soviet Union and the Russian Federation. United State’s recurring discord with Russia did not hinder the continuation of this strategic cooperation. CTR was a notable exception because it continued to be renewed every seven years for more than 20 years, even during the Kosovo crisis, Georgian conflict and other tensions between the U.S. and Russian Federation. The United States further expanded the Nunn-Lugar principles, norms and rules to other regions of world. It became a robust security regime by also addressing new types of threats. Nunn-Lugar eliminated bureaucratic and red tape burdens on the Defense Threat Reduction Agency throughout the post-Cold War. The Nunn-Lugar destroyed a chemical weapons stockpile in Albania. It is also given the resources and flexibility to work with countries such as Pakistan and trying to cooperate with North Korea if a future agreement allows it. Nunn-Lugar has expanded so as to provide nuclear security by assisting countries in securing fissile material and nuclear weapons, and supporting countries countering attacks concerning weapons of mass destruction. In 2002, Nunn-Lugar model has been adapted by Global Partnership Against Weapons of Mass Destruction by G-8 countries in Canada. In this context, 23 industrialized countries joined forces to dismantle nuclear submarines and eliminate chemical weapons in Russia. NunnLugar as well as other initiatives such as Global Partnership is still in force and will be renewed for another 10 years.