Kennedy was right when he asserted in 2002 that North Korea likely already possessed nuclear weapons. The U.S. intelligence community has judged since 1993 that North Korea extracted sufficient weapons-grade plutonium from the Yongbyon nuclear reactor in the late 1980s and early 1990s to build one to two nuclear weapons. The Agreed Framework came about in 1994 to prevent the Norks from extracting additional plutonium. It has always been an open question, however, if the North Koreans had the technical know-how to build a nuclear weapon--never mind how much plutonium they extracted. That question was only definitively answered last fall with the nuclear test.
Yet none of this diminishes the stupidity of the Bush Administration's actions in 2002. So long as the Agreed Framework held, the Norks could not extract any more plutonium from Yongbyon and were essentially capped at one to two weapons, assuming they were able to successfully weaponize the fissile material. When we abandoned the Agreed Framework, the North Koreans in 2003 and 2004, effectively quadrupled the size of their fissile stockpile. There is a HUGE difference between one to two nuclear weapons and six to eight nuclear weapons. For one, it is tough to test a weapon if you are surrendering half of your inventory. (A joke in the 1990s was that the most effective U.S. response to a NK nuclear test would be to encourage them to conduct another test right away.) Second, with six to eight weapons, suddenly it becomes so more tempting to sell one or two weapons to a terrorist group or another regime. Third, six to eight weapons begins to move North Korea towards having a real nuclear deterrent-