I don't mean by this that one must wage war against the unbelievers until they submit or are punished for their unbelief. Or that nations should submit to injustice or lie down in the face of aggression.
I mean that there can be no true peace and justice without true conversion of hearts. Until all men order themselves to God, there can be no lasting peace. It also seems to me that the common good of all mankind cannot be in the custody of some "supranational" authority, but its care belongs to God alone, and nations must respect the Eternal Law when dealing with one another. If a nation offends the "international" common good, is it necessary that there be a supranational authority to punish it? It seems not--it seems that any other nation would have the right to oppose it, and to use force if necessary. But I need to think about this more.
Can there be an international authority, created by all nations ceding their sovereignty? I don't think so, but I will have to elaborate later.
I would entertain the claim that the appropriation of the OT symbols of the dove and of the olive branch by secular institutions is a possible failure to recognize God's sovereignty and authorship of the created order. No doubt there are good men who are involved with the United Nations, but I do have a suspicion that the world is still under the sway of the devil, and even if an ideal political order could be established (through grace), it might not last long because of all that opposes God.
Does this mean that evil is greater than good? I don't admit that it is; however, I do think that God permits sin to happen, and there is much sin in the political realm.