A friend and former student of mine used to like to argue with me that Kant's work supported the American "intervention" in Iraq and the more general neoconservative project of "exporting" democracy around the world, because only in such a world would peace be possible. Of course, I'm no Kantian, so I wasn't precisely sure why that was supposed to convince me of anything.
Today, in reading Kant's "Perpetual Peace" to prepare for class, I was reminded of how strange and silly it is to think that Kant's sketch of peace could be used to justify war—particularly inasmuch as he is concerned in this essay to undermine the very notion of a just war. Kant does think that perpetual peace is only possible in a world of republics—not democracies, of which he is not particularly fond, thinking them naturally despotic—but he is adamant that there can be no justification in invading another country in order to change its internal structure, no matter what that structure may be—no overthrowing Husseins or Allendes—except in a very few cases. And, one of his most stringent conditions is that there be no relations of debtor and lender between states. Combined with his claim that the inability of sovereign states to put themselves under another authority is one of the highest bars to peace, it is hard to see exactly how he can be drafted to this particular cause.