Ius gentium and the right to migrate: a historical retrieval of the Spanish Scholastics (Part 1: Francisco de Vitoria)

Author: Antônio Lemos

This essay explores the concept of ius gentium in the 16th century Spanish scholastics as a conceptual tool to understand the right to migrate as promoted in recent Catholic social teaching as a flexible norm that retains a close link to natural law. Theologian Daniel Groody points out that civil law in migration ethics studies should not be understood as a separate reality. For this reason, he argues that it is the job of theology to remember that civil law is deeply connected to the eternal law, which is God’s loving plan to the universe, and the natural law, which is how the human person discovers God’s plan for herself. In this context, the law of nations, which is the main subject of this essay, is a bridge between civil law and natural law.

Pope Pius XII
Pope Pius XII

Pius XII was the first pope to argue for the existence of a “right to migrate” in the apostolic constitution Exsul Familia of 1952. He claimed that this right to cross political borders was based on the universal destination of goods, the theological principle by which we understand that God created the earth for the flourishing of all human beings.

Later on, John XXIII articulated the right to migrate among the fundamental rights due to the human person, but for the first time put a limit to it by saying that it was conditioned by “just reasons”. John Paul II followed this lead and clarified that this was not an absolute right, meaning a right that cannot be limited by the state like the right to live, and it should be in harmony with the common good and the duty of the state to protect its borders.

The Church’s approach to the right to migrate represents a midterm between a non-border policy, where the right of migration would be practically limitless; and policy restrictions that make legal migration virtually impossible. Current theological reflection on migration ethics emphasizes the right to migrate, while downplaying regulation policies based on sovereignty, border security, and common good of host communities. The main problem is how to understand this law as a fundamental human right grounded on the universal destination of goods and the dignity of the human person, while maintaining the need for regulation. How can we protect the rights of migrants while conciliating it with the good of the host society?

In order to provide some conceptual tools to answer this question and understand this “non-absolute right to migrate”, this essay will turn to the historical retrieval of the Spanish scholastics. They addressed the problem of human mobility of their time using theological and legal concepts. The 16th century witnessed large migration movements across the globe fueled by colonization, poverty, trade, and missionary work. In this context, Francisco de Vitoria presented the “right to travel” as the right of free passage to move and dwell in foreign territory. This right was limited by certain conditions. He identified it under the legal category of “law of nations”, an idea inherited from the Roman jurisprudence tradition through Thomas Aquinas. This type of norm was rooted in natural law, while being flexible enough to be applied according to the circumstances of time and place.

Francisco Suarez follows Vitoria by providing a rich study of ius gentium. Although he does not directly address the right to travel, his systematic analysis can help shed more light to the way the Spanish scholastics used the concept of law of nations.

For this reason, this essay presents the Spanish scholastics as offering a synthesis of theological thought on the law of nations applied to human mobility. The notion of ius gentium is a powerful moral category that helps us to understand the natural law origin of the present day concept of right to migrate. Moreover, it shows why such a right should be applied according to the concrete circumstances of each society in line with the common good. This essay will analyse the way these two theologians understood ius gentium and how they saw its relation to natural law while being a flexible norm. Our goal is to use the concept of law of nations to understand Catholic Social teaching on migration and apply it as a theological principle to current migration policy. The first part of the essay will engage with Vitoria, and the second part with Suarez. 

Francisco de Vitoria


Francisco de Vitoria is one of the great figures of the second scholastics in the 16th century. He was a Dominican friar who taught theology at the University of Salamanca in the first half of the 1500s. Influenced by Aquinas and the Roman legal tradition, he dealt with the idea of ius gentium in many of his works. In the lecture “On the American Indians” Vitoria connects this idea of law of nations with the right of travel. This right, which is similar to our concept of the right to migrate, meant that people were free to move across territories granted that they did not cause harm to anyone. In the lecture, Vitoria analyzed the justice regarding the possibility of just war by Spaniards against natives in the Americas in the context of the colonization of the New World. He examines different titles by which the colonizers could wage war. While it could sound that Vitoria is trying to legitimize colonization, he is actually placing severe limits to European expansion and implicitly arguing for native’s rights and autonomy. For instance, he claims that Papal or Imperial authority does not include political power of the natives' territory.

One of the titles that Vitoria deems just is the violation of the right to hospitality and to travel by the indigenous people. According to him, those rights are based on the law of nations and to break them without a justification would open the possibility of war and appropriation of land. Again, Vitoria limits the kind of hospitality to which the Spaniards are entitled. For example, they are not entitled to hospitality if they harm the natives in any way.

But, what exactly is the law of nations in this context? First, Vitoria argues that the law of nations derives from natural law. This argument is drawn from the ancient Roman law code called “Justinian institutes”. In this sense he uses the sentence “what natural reason has been established among all nations is called the law of nations”. This is very relevant information regarding Vitoria's understanding of ius gentium. For him, this type of law is not merely a norm that is common to the nations, but it has its origin in the natural law. In a way, Vitoria is open to the possibility that certain laws of nations could be, properly speaking, natural law itself. We clearly can see this connection between natural law and the law of nations when Vitoria explains why citizenship is part of the law of nations. He claims that the proof of confirmation that citizenship is a right sustained by ius gentium comes from nature. He invokes the natural characteristic of man as a “civil animal”, a creature that pertains to a community and hence is entitled to citizenship in a community. He concludes that the status of not having any citizenship is in conflict with both the natural law and the law of nations.

The second relevant piece of information that Vitoria provides regarding the concept of ius gentium is that it is a law common to all nations. He explains that “amongst all nations it is considered inhuman to treat strangers and travelers badly without some special cause, humane and dutiful to behave hospitably to strangers. This would not be the case if travelers were doing something evil by visiting foreign nations”. Therefore, besides having origin in the natural law, ius gentium can be identified by its presence in the legal systems of all or most societies. Its extent includes even the inhabitants of the New World and their communities, as Vitoria constantly reminds us throughout the text. This is a very important note, since later on Suarez showed himself very skeptical regarding the idea of an universal law of nations. For him, this type of law is too dependent on human consent.


From Vitoria's argument, we also gather that he believes that the ius gentium is not absolute, or at least has not the same necessity as that of natural law. He points out that the Europeans have the right to trade and travel “as long as they do not harm” the indians. Hence, there are circumstances in which the right to travel as a law of nations should not be applied, especially in those cases when any type of harm is being produced against the host nation.

When talking about divine and natural law, Vitoria mentions in two occasions that a human law that goes against it would lose the force of law. For example, if the right to travel is understood as divine and natural law, then it would be unjust to enact a human law that forbids foreign travelers in one’s territory. Vitoria never makes the same kind of precision regarding the law of nations. It seems that a community could enact a law that goes against the law of nations, if this law of nations is not a divine and natural law itself. We can imagine that the law of nations in this case could still be derived from the natural law, but not properly speaking be the natural law itself. For this reason, it would be easier to change the law of nations.

Does a violation of the law of nations automatically legitimate a coercitive action to enforce it? Vitoria thinks that first rational persuasion should be employed in order to secure compliance with ius gentium. He argues that once non-violent means are used to convince and persuade without avail, then war and proportional violence can be employed to enforce the law. This shows us the rational element of the law of nations, which should be recognized by any human being. In this sense, Vitoria is very optimistic about the universal character of the ius gentium.

Vitoria's exposition of ius gentium in “De Indis” is not systematic. He employs the concept of law of nations in order to explain the rights of travel, dwelling, trade, and citizenship. It is difficult to understand if this concept is part of natural law or positive law. Sometimes they seem to coincide, and in other moments he draws a hard line between them. Moreover, it is ambiguous how one should proceed in order to verify whether a particular law is part of the ius gentium.

In spite of these problems, Vitoria’s treatment of ius gentium helps us to understand that the law of nations is first of all truly a law. Further, it is a universal law common to the commonwealth of nations. It has its origin in natural law, but it is not similarly biding. Finally, the law of nations is not absolute, it can be changed and overridden by human law. In the next part of the essay we will examine Suarez’ contribution to this debate. 

Suggested further reading

Vitoria, Francisco de, Pagden, Anthony, and Lawrance, Jeremy. Political Writings. “On the American Indians” and “On Just War”, “De Temperantia” Cambridge [England] ; New York: Cambridge University Press, 1991

Lantigua, David M. 2021. Infidels and Empires in a New World Order : Early Modern Spanish Contributions to International Legal Thought. First paperback edition.. Cambridge, United Kingdom ; New York, NY, USA: Cambridge University Press.

Cavallar, Georg. 2002. The Rights of Strangers : Theories of International Hospitality, the Global Community, and Political Justice Since Vitoria. Aldershot, England ; Burlington, Vt.: Ashgate.

Tellkamp, Jörg Alejandro. 2020. A Companion to Early Modern Spanish Imperial Political and Social Thought. Leiden ; Boston: Brill.

About the author


Antonio Lemos

Antônio Lemos hails from Curitiba, Brazil. After studying law at the Universidade Federal do Paraná, he graduated in philosophy and theology at the Pontifical Athenaeum Regina Apostolorum in Rome, Italy. It was there that he attained a degree in licentiate in sacred theology (equivalent to a master's degree), with a specialized focus on moral theology and Catholic social teaching. His licentiate dissertation bore the title “Perspectivas morais do fenômeno migratório no magistério recente” (Moral perspectives of the migratory phenomenon in the recent Magisterium). Presently, he is engrossed in the pursuit of a Ph.D. in moral theology from the University of Notre Dame. His ongoing research journey navigates the right of migration as laid out in Catholic social teaching and the traditions of Christianity. He holds a particular fascination for the theological and moral principles that serve as the bedrock of this right, while also tracing its historical origins, with a keen eye on the sixteenth and seventeenth-century Spanish scholastic influences. His other interests include virtue ethics, economics, business ethics, and bioethics. When Antonio is not studying, he enjoys drinking IPAs, listening to German heavy metal, and playing Dungeons and Dragons with fellow theologians.