The Proliferation Security Initiative (PSI) is a global effort that aims to stop trafficking of weapons of mass destruction (WMD), their delivery systems, and related materials to and from states and non-state actors of proliferation concern. Launched by United States President, George W. Bush in May 2003 at a meeting in Kraków, Poland, the PSI has now grown to include the endorsement of 105 nations around the world, including Russia, Canada, the United Kingdom, Australia, France, Germany, Italy, Argentina, Japan, the Netherlands, Poland, Singapore, New Zealand, Republic of Korea and Norway. Despite the support of over half of the Members of the United Nations, a number of countries have expressed opposition to the initiative, including India, China and Indonesia. History The idea of the PSI is generally credited to John R. Bolton, former US Under-Secretary of State for Arms Control and International Security and former United States Ambassador to the United Nations, after 15 Scud missiles found on board an unflagged North Korean freighter, the So Sen, heading towards Yemen had to be released when it turned out that international law did not allow them to be confiscated. Given this apparent gap in international law, several months later US President Bush announced the initiative with his counterpart, Polish President Aleksander Kwaśniewski at Wawel Castle in Kraków on May 31, 2003. Initially, the PSI included 11 "core" states (Australia, France, Germany, Japan, the Netherlands, Portugal, Spain, the United Kingdom, the US and Poland). On September 4, 2003, in Paris, these countries detailed the principles governing the PSI in a document titled the "Statement of Interdiction Principles". The document defines the activities which are to be undertaken by the initiative, specifically "to establish a more coordinated and effective basis through which to impede and stop shipments of WMD, delivery systems, and related materials flowing to and from states and non-state actors of proliferation concern, consistent with national legal authorities and relevant international law and frameworks, including the UN Security Council circumstances in which such operations may be carried out (at sea, on land, or in the air) including, most importantly, the requirement that any action taken must be consistent with international law." Since the initial core group of 2003, PSI has expanded to include an "Operational Experts Group" (OEG) of 21 nations as well as 84 other endorsing states. Key states who have endorsed the initiative since its initial founding include major