Robert Koons reviews just war theory:
A formal declaration of the intent to wage war on the part of the Senate, along with a specific set of demands, must precede any U.S. military action. Iran must be given the opportunity to avoid war by ending its support of terroristic and other unjust aggression against Israel, and by recognizing Israel’s right to exist and right to a peaceful, negotiated settlement of the rights of Palestinians. If these conclusions are correct, then it would be wrong, not only for the United States to engage at this time in an attack on Iran, but also for it to participate substantially in an Israeli action (by knowingly providing the aid, arms, or technical support required, whether overtly or covertly).
I'd also argue that pre-emptive war based on an enemy's alleged intentions, when it publicy declares the opposite, or based on inherent evil or insanity is counter to just war theory. Certainly the rhetoric of Santorum and Gingrich on this subject is a profound attack on Catholic just-war teaching. But don't expect the Bishops to make any fuss about that. War and torture seem trivial issues to them, compared with access to contraception or gay rights. R.R. Reno pushes back against Koons:
I think Koons misconceives the political importance of Congressional declaration of war with a moral importance. Our constitutional constraints on the declaration of war are legal mechanisms designed to ensure accountability and prevent our President from conducting private wars that do not serve the national interest. Formal declaration of war brings our foreign policy above board. Yes, that would clarify things for the Iranians, but as I observed we can make things clear in other ways.
The real importance is domestic. Citizens need to know when our leaders have committed military force, because at the end of the day it’s our blood and treasure that’s on the line. That’s not to say that a preemptive strike against Iran would satisfy other just war criteria, but it does suggest that Koons reasoning is a bit too legalistic and not altogether convincing.