The Proliferation Security Initiative (PSI), launched initiated by US President Bush in May 2003, was designed to prevent elements of weapons of mass destruction (WMD) from reaching or leaving states or sub-state actors of proliferation concern. More than twenty countries now adhere to PSI principles.

Though the principal focus of the initiative is on North Korea, Japan and Singapore are the only active East Asian participants. Most WMD traffic moves by sea, and the focus of the PSI is on maritime interdictions and seizures. Although the PSI has had some significant successes, its...