Daniel Larison calls out the cafeteria Catholics at First Things* for rejecting Church teaching on the immorality of "preventive war." Since all states potentially threaten their neighbours, if war could be justified on the basis of "prevention", then all aggressive wars would be preventive ones. Therefore, the Vatican's position is a necessary implication of holding on to any just war theory at all. The point is a so obvious, one despairs that Larison has to make it. But he does, and does it with his characteristic erudition, so I commend it unto you.
I also commend Matthew Yglesias's response to Dennis Ross. Ross thinks it makes sense to impose, as a precondition on negotiations with Abbas and Fatah, that they prevent any attack on Israel by their sworn enemies in Hamas. Yglesias makes the obvious point that imposing such conditions would make it trivially easy for Hamas to prevent any negotiation from occurring. The fact that Ross was Clinton's main man on the Israel-Palestine dispute and Yglesias is a snot-nosed kid may explain why the situation in the Middle East has gotten as bad as it has.
*Since they have rejected "Thou Shalt Not Kill" (Fifth by the Catholic numbering) in favour of Reagan's Eleventh Commandment.
Update After 14 comments: I think the discussion has been interesting. In the end, Andy seems (to me) to retreat from arguing that preventive war is justifiable to arguing that the war was necessary to enforce the peace terms Iraq accepted after 1991. I disagree "on the facts", but I accept that such a justification isn't in principle contrary to the just war tradition.
But while I recognize that some arguments along these lines were advanced, the Bush administration clearly did present itself as putting forward a new doctrine. Lee at Thinking Reed has the goods.
Further Update: On the Internet, you can even get a discussion by an "Independent Catholic Priest" on how Augustine's comments on the Third Punic War anticipate the arguments about Iraq. (Via Thinking Reed)