Rising authoritarianism, armed conflicts, and technological upheaval are eroding the foundations of international law. One state, with no army, no economic might, and physically smaller than many college campuses, continues to exert global influence through the quiet power of moral authority and legal advocacy. The Vatican, long underestimated as a relic of medieval diplomacy, arguably is a pivotal actor in defending the rule of law, human dignity, and ethical governance on the world stage. One of Pope Francis’s last official acts was to raise the status of the Vatican’s diplomatic academy to confer degrees in “diplomatic sciences.” Advanced training in international law, economics, and technology policy is now required. Every future nuncio (Vatican ambassador) must also now spend a year in missionary service.
Pope Leo XIV, a missionary-canon lawyer by training, has barely begun his pontificate, but he already finds himself confronting urgent tests that will define his approach to international law and diplomacy. Leo XIV’s first address to the Diplomatic Corps on May 16, 2025, sketched a three-pillar foreign-policy credo: peace, justice, and truth.
The first US-born pope faces four mounting crises: the ongoing conflict and humanitarian crises in Ukraine and Gaza, an aggressive bid by China to control the Church, artificial intelligence ethics, and migration in the Americas. Each issue places the Holy See squarely at the intersection of diplomacy, human rights, and the survival of a rules-based international order.
From Neutrality to Norms in Ukraine and Gaza
The war in Ukraine presents Leo XIV’s first and most immediate test. Departing sharply from the neutrality that characterized much of Francis’ diplomacy which left many Ukrainians confused, the new pope has embraced the language of international law. Shortly after stepping onto the loggia of St. Peter’s Basilica on May 11, 2025, reflecting on how he carried in his heart “the sufferings of the beloved Ukrainian people,” he called Ukrainian President Volodymyr Zelenskyy to discuss a “just and lasting peace” and the thousands of deported Ukrainian children by Russia.
Significantly, when Leo XIV was still Bishop of Chiclayo in Peru, he described Russia’s actions in Ukraine as “a true invasion, imperialist in nature,” stressing that Russia’s actions are driven by a desire for power and strategic dominance. He affirmed that “crimes against humanity are being committed in Ukraine” and urged for greater moral clarity in confronting the conflict, noting that “some leaders in our own countries still avoid acknowledging the evil of what is happening there.”
Whether Leo XIV will continue these views as pope and direct future Holy See communiqués to openly characterize Russia’s actions as “aggression” and emphasize Ukraine’s “territorial integrity” is yet to be seen, but Holy See diplomacy would mark a significant shift if it decides to invoke precisely the legal language enshrined in Article 2(4) of the United Nations Charter, which prohibits the use of force against the territorial integrity or political independence of any state.
By choosing these terms, Leo XIV would signal a realignment of Holy See diplomacy with the legal foundations of the postwar international order. Jus ad bellum, particularly the fundamental prohibition against aggressive war, would once again come into focus for the Vatican as a recognized jus cogens norm of international law. The Holy See’s invocation of these norms positions it firmly alongside states and organizations including the European Union and the Organization for Security and Co-operation in Europe (OSCE), that have condemned Russia’s invasion as illegal under international law.
However, this pivot carries risks. While the Holy See could gain support from the West and Ukraine, Moscow could significantly limit diplomatic relations, complicate the Holy See’s ability to mediate humanitarian issues such as prisoner exchanges and potentially endanger Catholic communities within Russia. Yet by stepping clearly onto the side of law, the Holy See asserts that peace must respect legal norms that safeguard human dignity and sovereign rights.
Leo XIV also urged for a ceasefire and the release of hostages in Gaza, saying, “I am deeply saddened by what is happening in the Gaza Strip: may there be an immediate ceasefire! Let humanitarian aid be provided to the stricken civil population, and let all the hostages be freed.”
Leo XIV’s tone marks a departure from Francis’s sharper rhetoric, which included calls to investigate potential genocide, a jus cogens violation, in Gaza. Leo XIV chose a more restrained approach by avoiding reference to genocide and war crimes. Instead, he focused on immediate humanitarian needs and pledged to continue “dialogue and cooperation with the Jewish people.” Israeli Prime Minister Benjamin Netanyahu’s congratulatory message suggests cautious optimism that Holy See-Israel relations may stabilize under the new papacy.
Positioning himself as a neutral moral voice, Leo XIV may emphasize the Geneva Conventions and humanitarian corridors without direct legal confrontation. Though silent on the Israel-Palestine issue as a cardinal, his background as a missionary and advocate for social justice suggests he will continue the Vatican’s emphasis on quiet diplomacy and humanitarian engagement in the region.
Leo XIV’s education at the Catholic Theological Union, known for its interfaith emphasis, and his experience in Peru defending migrants and marginalized groups suggest he will prioritize interreligious dialogue and refugee protection in the Middle East. This would include deepening ties with moderate Sunni and Shia Muslim leaders, continuing the principles of the Abu Dhabi Document on Human Fraternity, and advocating for humanitarian corridors and refugee rights.
Leo XIV may also pursue pragmatic cooperation with Gulf States like the UAE, Qatar, and Saudi Arabia, capitalizing on goodwill established during Francis’s visits and the Abraham Accords framework to promote Muslim-Christian-Jewish understanding and facilitate backchannel diplomacy across Sunni-Shia lines.
China, Canon Law, and the Erosion of Sovereignty
While issues surrounding Ukraine and Gaza focus on legal standards in wartime, China presents an even more complex and delicate test of religious soverignty.
In the days following Francis’ death, and while the Holy See remained incapacitated to appoint bishops during the sede vacante, Chinese authorities moved swiftly to “elect” Father Wu Jianlin as auxiliary bishop of Shanghai by a local assembly of state-affiliated clergy in violation of Code of Canon Law 377 §1. The very next day, Father Li Jianlin was selected as bishop of the Diocese of Xinxiang despite the Vatican’s longstanding recognition of Bishop Joseph Zhang Weizhu, who has spent decades ministering underground and remains imprisoned without trial.
These appointments, conducted unilaterally and without Vatican ratification, directly violate the spirit—and arguably the letter—of the highly criticized 2018 Provisional Agreement between the Holy See and Beijing, last renewed in 2024. Although the full terms of the agreement remain secret, reports confirm that it was designed to establish a joint consultation mechanism for the appointment of bishops. Bishops would be nominated locally in China, but the pope retains final authority to approve or veto episcopal appointments. In exchange, the Chinese government unofficially agreed to acknowledge the pope’s supreme authority over the Catholic Church in China.
Beijing’s preemptive moves, particularly during a period when the Vatican was unable to act, raise serious concerns about bad faith, a principle explicitly recognized in Article 26 (“Pacta sunt servanda”) and Article 18 (obligation not to defeat the object and purpose of a treaty) of the Vienna Convention on the Law of Treaties (VCLT) in binding treaties. The principle remains normatively important even in the context of nonbinding political accords.
Beyond treaty law, China’s actions raise grave international human rights issues. The right of religious communities to govern themselves independently of state interference is enshrined in the Universal Declaration of Human Rights and elaborated in the International Covenant on Civil and Political Rights. China’s attempt to consolidate full control over the Catholic Church within its borders, including recent regulations banning foreign clergy from conducting religious activities without government approval, stands in direct violation of these principles.
Moreover, the symbolism surrounding these events underscores the depth of the rupture. Following Francis’ death, official Catholic bodies in China offered only perfunctory acknowledgment of his passing, focusing instead on commemorations of the 76th anniversary of the communist victory in Nanjing and acknowledging his death nearly 24 hours after the pope’s passing.
The Vatican now faces a stark diplomatic choice. Leo XIV could seek to renegotiate the China agreement, demanding measurable human rights benchmarks and public transparency for future bishop appointments. Alternatively, he could pursue a more confrontational approach, raising China’s religious freedom violations before UN Special Rapporteurs and human rights forums. There is also the possibility of a renewed focus on the Western Hemisphere, where Leo XIV’s connections with Latin American bishops, North American Church leaders, and European figures from his tenure as Prefect of the Dicastery for Bishops give him strong diplomatic and ecclesial relationships to build upon. He is more ideologically and culturally aligned with democratic, rights-respecting regions and may assess that the political cost of deeper engagement with Beijing outweighs the pastoral benefits.
Either path will test Leo XIV’s resolve to defend religious sovereignty through the mechanisms of international law rather than through Francis’s quiet, accommodationist diplomacy.
Redefining Papal Leadership in the Age of Artificial Intelligence
In his first formal address to the College of Cardinals after his election, Leo XIV zeroed in on the ethics of artificial intelligence while sharing the deeper meaning behind his chosen name, a clear nod to Pope Leo XIII and a deliberate gesture linking past and present in the Church’s mission for social justice.
“Pope Leo XIII, with the historic Encyclical Rerum Novarum, addressed the social question in the context of the first great industrial revolution,” he explained. “Today, the Church offers to all her treasure of social teaching in response to another industrial revolution and the developments of artificial intelligence.”
Under Francis, the Vatican emerged as a global leader in AI ethics. The launch of the Rome Call for AI Ethics, a multistakeholder pledge backed by Microsoft, IBM, and academic institutions in 2020, marked the Holy See’s efforts to humanize technology. Francis further raised the issue to the world stage during his 2024 G7 address, describing AI as a “cognitive-industrial revolution” on par with the transformative shifts of the 19th century. In early 2025, just a few months before his death, he issued Antiqua et Nova, a doctrinal note warning against dehumanizing automation and affirming the Church’s commitment to human-centered technology.
This concern is not abstract. Parents worry about misinformation spreading on social media, teachers face rising student cheating, and workers fear being replaced by robots. Leo XIV, who holds a degree in mathematics and has long been engaged in internal Vatican discussions on digital ethics, appears uniquely positioned to address both the technical and human dimensions of the issue. His thinking on technology dates back more than a decade. As he noted in a 2012 interview, the answer isn’t to reject media but to “teach people to become critical thinkers” and to “understand that not everything you hear or everything you read should be taken at face value.”
Early signals from Leo XIV suggest building on Francis’s legacy by advancing aspirational guidelines toward enforceable norms inspired by Catholic social doctrine. Some online sources have speculated that Leo XIV views the regulation of artificial intelligence as a core part of the Church’s mission, proposing that an encyclical on AI and labor could serve as a powerful vehicle to articulate a Catholic legal-ethical framework for AI governance. Even before such a document is issued, there are already existing legal mechanisms that Leo XIV could engage with or seek to influence.
He may seek to influence existing legal instruments, including the UN treaty on AI, by advocating for the inclusion of “human agency override” clauses to ensure that all high-risk AI systems retain mechanisms for human control and accountability. This would align Vatican policy with the efforts of the Council of Europe. The Holy See’s legal office might submit formal positions to treaty-drafting bodies, calling for enforceable obligations on transparency, explainability, and redress in AI deployment.
Echoing concerns raised in Antiqua et Nova, Leo XIV should condemn the development and deployment of lethal autonomous weapons systems (LAWS), arguing they violate key principles of international humanitarian law, such as distinction, proportionality, and moral accountability. In keeping with the Church’s just-war tradition, the Holy See will likely advocate for a preemptive international ban on fully autonomous weapons, similar to its past support for treaties banning landmines and nuclear weapons, and frame such technology as morally unacceptable and legally dangerous.
Jus Cogens and the Right to Migrate: The Moral Imperative to Welcome the Stranger
As the first American pope, a former missionary bishop in Latin America, and the descendant of immigrants, Leo XIV brings both pastoral sensitivity and doctrinal clarity to the migration crisis in the Americas. He inherits traditional Catholic teaching that frames migration as a human right. In 1963, Pope John XXIII in Pacem in Terris said, “[E]very human being has the right to freedom of movement and of residence within the confines of his own State. When there are just reasons in favor of it, he must be permitted to emigrate to other countries and take up residence there,” a right grounded in the person’s membership in “the universal society, the common, worldwide fellowship of men.” Similarly, Rerum Novarum insists that “when there is question of defending the rights of individuals, the poor and badly off have a claim to especial consideration.”
Leo XIV may press for a renewed international consensus on the rights of migrants. He could call for expanded recognition of migration as a matter of jus cogens. He may also push for broader adherence to and reform of the 1951 Refugee Convention to recognize newer categories of migrants, such as those fleeing economic collapse or environmental degradation. This would echo Francis’s Laudato Si’s warning that “the growing poverty caused by environmental degradation” leaves migrants without “any legal protection whatsoever.”
Leo XIV may also urge states to adopt or strengthen participation in regional frameworks such as the Cartagena Declaration on Refugees (1984), which recognizes generalized violence and massive human rights violations as grounds for asylum, a particularly relevant standard for Central America’s Northern Triangle and parts of the Caribbean. Drawing on the emphasis in Francis’s third encyclical Fratelli Tutti on human fraternity and “full citizenship,” Leo XIV could push for international consensus on equitable access to documentation, healthcare, and labor protections and move beyond the voluntary norms of the Global Compact for Safe, Orderly and Regular Migration toward binding international commitments.
For Leo XIV, protecting migrant families is not just good policy, it’s doctrinal. Catholic social teaching holds the family as the cornerstone of human dignity and social order, a principle repeatedly affirmed in documents like Gaudium et Spes, which urges authorities to help migrant workers “bring their families to live with them and to provide themselves with a decent dwelling.” Building on this, Amoris Laetitia warns that forced migration “traumatizes people and destabilizes families.” Leo XIV can urge governments to reject policies that detain or deport parents and children separately. He should call for legal safeguards that prioritize family unity in asylum processing and repatriation, framing such measures as humanitarian necessities and moral obligations.
Institutionally, he may also urge that arbitrary detention of migrants and asylum seekers be treated as violations of international humanitarian and human rights law. Additionally, he might renew calls for humanitarian corridors, as endorsed by Vatican delegations in past UN summits, especially for children and victims of trafficking. Leo XIV’s migration diplomacy could center on ensuring that states uphold their obligations under Article 33 of the Refugee Convention, which prohibits refoulement. Using his connections to the Americas, Leo XIV could advocate for these reforms in the UN and the Organization of American States (OAS) as a test of these institutions’ commitment to human dignity, solidarity, and the rule of law.
A Papacy at the Crossroads of International Law and Conscience
Behind all the pageantry and rituals, the Holy See remains a pivotal actor in the evolving architecture of global governance. Whether confronting violations of sovereignty in Ukraine, advocating humanitarian protection in Gaza, defending religious autonomy in China, regulating AI, or responding to migration across the Americas, Leo XIV is stepping into a role that demands principled action.
Leo XIV brings to the papacy the heart of a missionary, the training of a theologian and canon lawyer, and the voice of a pastor. His task will be to uphold the Church’s oldest traditions while confronting the world’s newest challenges, from war crimes to immigration to AI ethics. Leo XIV’s pontificate may yet offer an unexpected and timely reminder: that enduring authority in world affairs does not always come from hard power. Sometimes it comes from a higher law—the kind written not only in treaties, but in conscience.
