What is PSI?

The Proliferation Security Initiative is an international effort to interdict the transport of banned weapons and weapons technology. It is focused on combating the proliferation of nuclear, chemical and biological weapons and materials through proactive action and collaboration between member countries.

The Proliferation Security Initiative works with existing laws: it does not grant any new legal authority to undertake interdictions in international waters or airspace. Any action taken under the Proliferation Security Initiative must be in line with both domestic and international law. It is not a stand-alone initiative but rather complements and builds on efforts by the international community to prevent proliferation.

The Proliferation Security Initiative is a set of activities that countries engage in, not an organisation. There is no secretariat or organisation that acts as the governing body, no headquarters, no budget and no formal rules of procedure. Countries that endorse the Proliferation Security Initiative's Statement of Interdiction Principles determine their own degree of participation and cooperation is entirely voluntary.

Rather, members aim to share information between themselves and act when necessary to disrupt the trafficking of weapons of mass destruction. The Proliferation Security Initiative seeks cooperation from countries whose vessels, flags, ports, waters, airspace or land might be used for the spread of weapons of mass destruction and in the event of an interdiction. Instead of formal obligations, members commit to establishing 'best practices' to stop shipments of weapons of mass destruction and related goods.

Proliferation Security Initiative countries can share information, inspect suspicious cargo at borders, interdict (board) ships and impede the transport of weapons of mass destruction by air, as permitted by domestic and international law.

In a speech to the Madrid Summit in March 2005, former UN Secretary General Kofi Annan said
"I applaud the efforts of the Proliferation Security Initiative to fill a gap in our defences".