Mark Shea over at the National Catholic Register addresses the erroneous mental gymnastics Catholics in favor of preemptive war must pull to rationalize militarist politics:
The point is this: just war doctrine has been formulated by the Church, not to give us a trigger mechanism so that we can roll up our sleeves and commence slaughter with a song in our hearts, but in order to make it as hard as possible to go to war—because war kills innocent people. The point of just war doctrine, in other words, is to set up a series of roadblocks to slow down and restrain the human appetite for mayhem, vengeance, murder and destruction which sinfully yearns for an excuse to be unleashed. Just war doctrine is formulated in such a way that you have to fulfill all the requirements of just war teaching, not just one or two, in order to fight a just war. The first requirement is that all just war must be an act of defense against an actual aggressor, not a preventative act of aggression against somebody you fear might be an aggressor one of these days. Similarly, one of the criteria which must be fulfilled is that war must be a last, not a first, resort. Therefore, pre-emptive war is necessarily unjust war—because war is not something you “get” to do. War is something you tragically are forced to do as a last resort: like amputating your own leg. Pre-emptive war, being neither a response to an actual act of aggression nor a last resort is, itself, an act of aggression. It should be as morally desirable to Catholics as the thought of amputating one’s own healthy leg because you fear that in five years you might step on a nail and get gangrene. Not too eager to do that? Neither should any Catholic be eager to cut corners on just war doctrine—because war mean innocents will die, women will be made widows and children will be made orphans. That is why Joaquin Navarro-Valls, speaking on behalf of Pope John Paul II, said, “He who decides that all pacific means provided by the international law are exhausted, assumes a grave responsibility in front of God, in front of his own conscience and in front of history!”
In short, the argument that the silence of the Catechism on pre-emptive war is an argument in *favor* of it is like the argument that the silence of the Catechism on the subject of ritual cannibalism means that cooking and eating human beings in religious ceremonies is not “always wrong”.
Yes. It is. And so is pre-emptive war. That’s why it’s not in the Catechism.
Its actually pretty simple. Church doctrine isn’t about mere rules and regulations, it is a way of life and, when an individual stops asking, “how can I act in such a way as to always respect human life and dignity?” and instead approaches church teaching with the mindset of, “okay, how close can I toe the line and still get away without sinning?” Then you’ve already abandoned the spirit of the law. We don’t “get” to go to war. We are forced to engage in war only when it is necessary for our own defense, all other options have been exhausted and and we can do so without causing disproportionate or indiscriminate destruction. Going to war because our enemies might have WMDs is a violation of just war doctrine; going to war to “bring them democracy” is a violation of just war doctrine; going to war because a country we’re on bad terms with could be developing a nuclear weapon is a violation of just war doctrine. Period. End of story.