01 Overview
The CTBT was adopted by the UN General Assembly in September 1996 and opened for signature, but it cannot enter into force until all 44 states listed in Annex 2 (those with nuclear reactors in 1996) ratify it. Eight Annex 2 states have not ratified: USA, China, India, Pakistan, Israel, Iran, Egypt, and North Korea. Despite not being formally in force, the treaty has a remarkable monitoring network - the CTBTO's International Monitoring System (IMS) uses 337 facilities worldwide (seismic, hydroacoustic, infrasound, and radionuclide stations) to detect any nuclear explosion anywhere on Earth. The last confirmed nuclear tests were North Korea's in 2017.
02 Key Provisions
03 Why It Matters
The monitoring network has already proven its value - it detected every North Korean nuclear test. The political barrier (especially US Senate non-ratification since 1999) is the main obstacle to formal entry into force.