Just a quick point about Just War. According to Just War principles would the US and Allies have been justified in going to war with Hitler’s Germany had he not attacked any of his neighbors, but only set up concentration camps and committing genocide against the Jews? If so, can we not say we can be justified in going to war to defend those who are being murdered in totalitarian societies? Iraq is an example of such a state, with the murder of whole communities of Kurds and Shia Muslims and more.
In the Catechism 2263-2267, it speaks of legitimate defense. The context makes it clear that it is primarily about the defense of persons and societies, whether by an individual directly confronted by an aggressor or by the state preserving the common good of society. But what happens when the state itself is so disordered that it is the aggressor? Can we not say that it is imperative for a state composed of people of good will to come to the legitimate defense of the innocent in that disordered state for the good of society in a worldwide context? In the absence of a world government don’t we have a grave duty to defend the innocent of another sovereign nation, using peaceful means if possible, but using armed force if necessary?