"In 2003, President George W. Bush unveiled the Proliferation Security Initiative (PSI) in a speech in Krakow, Poland. The initiative was announced as a commitment among endorsing nations to prevent the spread of weapons of mass destruction (WMD) and their delivery systems. What started with 11 like-minded nations that endorsed the PSI Statement of Interdiction Principles had grown to 105 endorsers in 2016. This was achieved without treaties, ratifications, or other formal agreements as a basis for membership. The initiative continues to be based on a political commitment rather than on legal obligations. In the United States, what started in a Republican administration under President Bush continued to be supported by a Democratic administration led by President Barack Obama. With his Prague speech in April 2009, President Obama reiterated U.S. support of the PSI as an essential tool in U.S. foreign policy for fighting WMD proliferation. After 14 years and with a new administration, it is an ideal time to assess the PSI and consider its future in U.S. nonproliferation foreign policy. […]The purpose of this study was to gain a whole-of-government assessment of the PSI from the perspective of U.S. implementers."
National Defense University, Center for the Study of Weapons of Mass Destruction: http://wmdcenter.ndu.edu/