North Korean WMD Dragnet

The US and ten other nations have formed a cooperative agreement called the Proliferation Security Initiative that will focus on seizing weapons of mass destruction and missiles departing North Korea and destined for Europe. Also targeted will be "all states involved in the illegal trade of weapons." John Kerin, reporting for The Australian, states that:

"The meeting of diplomats in Madrid last Thursday endorsed the crackdown, under which ships would be stopped and aircraft forced down if they were suspected of trafficking weapons of mass destruction."

The article also states that a blockade was "considered risky because it could trigger a war" on the Korean peninsula.

This I don't understand. The "dragnet" to be instituted by the initiative does not seem to be substantially different from a blockade and the loonies that produce, sell, buy, and intend to use the weapons rarely need provocation for killing people.

One other thing, noticeably missing from the list of nations signing the initiative are the UK and South Korea.