NUCLEAR, BIOLOGICAL AND CHEMICAL WEAPONS
April 17, 2009: South Korea is joining the Proliferation Security Initiative (PSI), a six year old international agreement whereby participating nations agree to cooperate in halting the spread of WMD (nuclear, chemical and biological Weapons of Mass Destruction, including delivery systems). There are over 90 nations belonging to the PSI, although most only agree to get involved in a case-by-case basis.
The PSI is directed mainly against North Korea and Iran, and countries they might sell ballistic missile or WMD technology to. The most obvious PSI efforts involve stopping ships at sea and inspecting them. This has forced North Korea and Iran to move prohibited materials by air, which increases shipping costs considerably.
North Korea has said that South Korean attempts to stop and inspect any of its ships would be declared an act of war. South Korea, however, is fed up with North Korean double dealing and deception, thus the move to join PSI.