In the context of rising regional instability and conflict, along with increased incidents of global terrorism, in a dynamic, uncertain security environment, emerging nuclear and other weapons of mass destruction threats—both state proliferation and terrorism—are seen as growing dangers giving rise to increasing global insecurity. The international nuclear nonproliferation regime, the centerpiece of which is the Nuclear Non-proliferation Treaty (NPT), is essential to current and future non-proliferation efforts and needs to be maintained and strengthened, not replaced. The normative and legal weight of the regime is important for counterterrorism as well as non-proliferation, but it will not likely directly affect the behaviour of so-called ‘rogue states’ and terrorists. Preventing them from achieving their objectives if they attempt to wield nuclear and radiological weapons may deter and dissuade them, as may a credible prospect of punishment. The interaction of non-proliferation and deterrence, so clear during the Cold War history of the NPT, remain crucial parts of an increasingly complex picture.