Pope Leo XIV calls for AI regulation, repudiates 'just war' theory in landmark encyclical

Pope Leo XIV released a 43,000-word encyclical on Monday that amounts to the most forceful papal intervention in technology policy in modern history. Titled "Magnifica Humanitas," the document calls for governments to actively regulate artificial intelligence development, to prevent private companies from monopolizing AI data, to protect workers from exploitation, and to cool the competitive frenzy driving the industry forward. The pope, who has grown more vocal in recent months and drawn criticism from the Trump administration over his stance on the Iran war, framed the encyclical as a letter to Catholics and all people of good will—a signal that this is not merely internal Church teaching but a direct appeal to global leadership.

At the heart of the encyclical lies a simple but radical claim: the world is moving too fast. "What is needed is a more active political involvement that is capable of slowing things down when everything is accelerating," Leo wrote. He called for robust legal frameworks, independent oversight of AI systems, informed users, and a political system willing to exercise responsibility rather than cede it to market forces. The pope warned that AI systems spread misinformation, prioritize conflict, and risk pushing humanity toward perpetual war. He invoked the biblical Tower of Babel—humanity's prideful attempt to reach heaven without divine blessing—as a parable for the dangers of unchecked technological ambition.

The encyclical's most striking theological move was its repudiation of just war theory, a doctrine the Catholic Church has relied upon since at least the fifth century to evaluate whether armed conflict could be morally justified. Leo declared the theory "outdated" and said it had been invoked far too often to rationalize any war, including recent conflicts. The timing was pointed: Vice President JD Vance, a Catholic, had cited just war doctrine to defend the Iran war, which Leo had publicly criticized. The pope wrote that force, violence, and weapons reflect "a relational poverty that always has disastrous consequences for civilian populations." He also raised the specter of leaders using war as a distraction from domestic failure—a cynical tool for managing political difficulty at home.

On the specific question of AI in warfare, Leo was unequivocal: entrusting lethal decisions to artificial systems is "not permissible." Any military use of AI must be subject to the most rigorous ethical constraints. This stance puts the Vatican at odds with military establishments worldwide that are rapidly integrating autonomous weapons systems into their arsenals.

The encyclical also addressed labor and human dignity in the technology supply chain. Leo invoked his predecessor Leo XIII, who in 1891 called for better pay and conditions during the Industrial Revolution, and drew a parallel to what he called "new forms of slavery" in the modern tech industry. He specifically highlighted children and adolescents working in dangerous conditions to extract rare earth elements—materials essential to the computers and smartphones that power AI systems. "The bodies of these people are scarred, injured and worn down so that computational flow may continue uninterruptedly," he wrote. This reality, he said, "deeply challenges the moral conscience of our time."

In a moment of historical reckoning, Leo also acknowledged that the Catholic Church had failed to forcefully condemn transatlantic slavery until the nineteenth century. "This constitutes a wound in Christian memory," he wrote, and he offered a personal apology on behalf of the institution. The connection was implicit but clear: the Church's historical silence on slavery should inform its present vigilance against new forms of exploitation.

At the Vatican event presenting the encyclical, Chris Olah, co-founder of Anthropic—one of the world's leading AI companies and producer of the Claude AI tools—thanked the pope for addressing the problems posed by the technology. Olah acknowledged that frontier AI labs operate within incentive structures that can conflict with doing the right thing, and he suggested that outside scrutiny was necessary. His presence and remarks signaled that at least some in the industry recognize the legitimacy of the pope's concerns, even if they resist the regulatory framework he is proposing.

The encyclical arrives at a moment of intense tension between technological acceleration and democratic governance. Governments worldwide are struggling to regulate AI while companies race to deploy increasingly powerful systems. Leo's intervention is unlikely to slow that race, but it establishes a moral baseline: that human dignity, worker protection, democratic oversight, and the prevention of war are non-negotiable values that must constrain technological development. Whether world leaders and tech executives heed that call remains an open question.