Pope Leo XIV’s first encyclical, “Magnifica Humanitas” (Magnificent Humanity), the Catholic Church’s authoritative pastoral letter released on May 25, emphasized the need for “safeguarding the human person in the time of artificial intelligence,” including the use of AI in warfare and the threat posed by killer robots.
Building on the church’s long-held position, Pope Leo wrote that “the decision to use lethal force cannot be delegated to opaque or automated processes, but must remain under effective, self-aware and responsible human control.”
The previous pope, Pope Francis, addressed in 2024 the existential threat posed by autonomous weapons systems, warning that “no machine should ever choose to take the life of a human being.”
Both pontiffs have argued that surrendering lethal decisions to algorithms degrades human dignity, and that it insulates politicians and military leaders from the moral weight of their actions. Christian, Buddhist, and Muslim groups joined a 2023 interfaith statement calling for “urgent united action against killer robots.”
The Stop Killer Robots campaign, which Human Rights Watch co-founded in 2013, has called for a treaty with prohibitions and regulations on autonomous weapons systems. And now Pope Leo has appealed for “responsibility [to] … be clearly defined at every stage: from those who design and develop these systems to those who use them and rely on them for concrete decisions” to ensure that “the development and use of AI in warfare [is] subject to the most rigorous ethical constraints, to guarantee respect for human dignity and the sanctity of life.”
In June, states will meet at the United Nations to discuss for the first time how to address the “opportunities and challenges” posed by use of AI by militaries. States will meet again in Geneva in November to consider whether to formally launch negotiations for a treaty regulating the use of autonomous weapons systems. To date, 130 states have expressed support for a legally binding instrument prohibiting or regulating such weapons.
Undecided states should take into account the Vatican, other countries, and civil society organizations that have all spoken out on the unchecked rise of digital technology creating a real possibility that algorithms will be entrusted with life-or-death decisions. They should take immediate steps to regulate this technology to ensure that it serves—and doesn’t destroy—humanity.
