Pope Leo XIV’s “Magnifica Humanitas” warns that just war theory has too often been used to justify any kind of war and, in light of modern weapons and artificial intelligence, may be outdated. That intuition, disciplined by Christian theology, refined by natural law, translated into international law, and embodied in our Constitution, is called just war theory. One may respectfully disagree with the pope’s conclusion that just war theory is outdated. Just war theory does not end once war begins. Just war theory is one of the structures by which civilization restrains the violence it sometimes must employ.