The nub is, Cardinal Ratzinger said it all:
Your Eminence, a question about current events, in some way connected to the Catechism. Does the coalition war on the Iraq come within the canons of the “just war”?
RATZINGER: The Pope has very clearly expressed his thoughts, not only as the thoughts of an individual, but as the thoughts of a man of conscience occupying the highest functions in the Catholic Church. Of course, he has not imposed this position as a doctrine of the Church, but as the appeal of a conscience enlightened by the faith. This judgment of the Holy Father is convincing from a rational point of view also: reasons sufficient for unleashing a war against Iraq did not exist. First of all it was clear from the very beginning that proportion between the possible positive consequences and the sure negative effect of the conflict was not guaranteed. On the contrary, it seems clear that the negative consequences will be greater than anything positive that might be obtained. Without considering then that we must begin asking ourselves whether as things stand, with new weapons that cause destruction that goes well beyond the groups involved in the fight, it is still licit to allow that a “just war” might exist.