What is the just war theory that the pope says is 'outdated' and that Trump and Vance have invoked against Iran?

This Monday, Pope Leo XIV called the doctrine of just war advocated by the Trump administration is "outdated," claiming that humanity is falling into "a violent culture of power."

Since the war began in Middle East in February, the pope has sharply criticized the conflict, condemned President Trump's threat to destroy Iran as "truly unacceptable" and urged Americans to demand that their lawmakers "work for peace."

In his first encyclical, "Magnifica Humanitas," the pope wrote: "Today, more than ever, without prejudice to the right to self-defense in the strictest sense, it is important to reaffirm that the just war theory, which has all too often been used to justify any kind of war, is now outdated."

Leo XIV also noted that, instead of resorting to armed conflicts, the world has tools such as "dialogue, diplomacy and forgiveness" to resolve them.

Trump and Vance's counterattack on Pope Leo XIV

The Trump administration has repeatedly justified its attack on Iran as a way to prevent the country from developing nuclear weapons capability. In April, Trump branded the pope as "WEAK on Crime, and terrible for Foreign Policy," to which the pope responded that he had a "moral duty to speak out."

Vice President J.D. Vance has publicly defended the just war doctrine to justify military action against the Iranian regime. At a Turning Point USA (TPUSA) event held last month in Georgia, Vance urged the pope to be "careful" when speaking on theological issues.

Catholic defense of just war: "A virtuous act"

One of the most respected Catholic thinkers in the United States, Father Gerald Murray, an expert in canon law, has defended with solid arguments why, from the Church's doctrine, military action against Iran could be considered a just war.

In an article in The Free Press, Murray explains that "the Church is not pacifist in her doctrine." Since St. Augustine and St. Thomas Aquinas, the Catholic tradition has recognized that, in certain circumstances, resorting to arms is not only permissible, but can be "a virtuous act" to protect the innocent against an "unjust aggressor."

According to the priest, the attack on the Iranian regime was not simply a necessary defense measure. Iran has been acting as a bitter enemy of the U.S. and its allies for nearly five decades, funding terrorist groups such as Hamas and Hezbollah and threatening again and again to destroy the State of Israel. But the tipping point was the regime's nuclear program.

Iran's imminent nuclear threat: Murray's key argument

During the negotiations, envoys Steve Witkoff and Jared Kushner were surprised when the Iranians admitted they possessed 460 kilograms of 60% enriched uranium and that it could be taken to weapons grade in just a week.

For Murray, waiting for Iran to complete its nuclear weapon would have been morally irresponsible. Just war doctrine does not require that a nation receive the first strike if there is "a clear, grave and imminent threat." The Catechism of the Catholic Church allows "legitimate defense by military force" when certain conditions are met: it must have "serious prospects of success" and "the use of arms must not produce evils and disorders graver than the evil to be eliminated."

According to Murray, the war in Iran "meets the conditions."

Why Father Murray considers military action against Iran to be just

During negotiations, the U.S. offered Iran non-weapons-grade uranium for 10 years in exchange for abandoning its nuclear program. The Iranian response was a resounding no. That showed that their real intention was never civilian.

For Father Murray, the U.S. and Israeli military action against Iran's nuclear and military facilities meets the classic criteria of just war: it was a last resort, proportionate to the danger and sought to eliminate a concrete threat, not to conquer territory or destroy the Iranian people.

The debate within the church will continue, but Father Gerald Murray's position reflects an important strand of traditional Catholic thought that does not close its eyes to the real threats in today's world.