After topics like abortion and same-sex marriage, few subjects fuel more division than migration. That’s partly because of concerns about subjects such as Islamist terrorism, failures to maintain border security, or some American and European political and religious leaders’ apparent reluctance to acknowledge such phenomena as real problems. But it’s also a result of genuine apprehensions about the possibility of governments breaking up intact families, not to mention the compassion that we should have for those fleeing war, persecution, terrorism, and bleak economic futures.

Before, however, the specifics of these and other questions surrounding migration can be addressed, we need clarity about the origins, nature, and limits of national sovereignty. Some regard national sovereignty as a fading relic of a pre-globalized world. Yet the concept of national sovereignty provides an indispensable framework for any coherent response by legislators and citizens to the challenges—and opportunities—associated with the movement of individuals who, for many reasons, desire to reside permanently in countries of which they are not citizens.

Common Bonds, Common Good

On one level, the origins of national sovereignty are to be found in the fact that there exist groups of people who regard themselves as members of one national community rather than another. Thanks to factors such as a common culture, language, beliefs, shared memories, sense of a common patrimony, and association with a particular territory with recognized boundaries, Estonians, for example, understand themselves as belonging to the Estonian nation rather than the Dutch people.

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These shared bonds mean that members of that group not only consent to be governed by those charged with the responsibility of governing that nation; they are also prepared to make sacrifices for other members of the same nation. These range from defending their country from internal or external aggression to paying taxes in order to provide common services for the other citizens of their nation.

Put another way, French citizens are committed to the common good of France in ways that they are not committed to Italy’s common good. This is despite the fact that many Italians live along France’s southern border and are geographically closer to French citizens who live in Marseilles than are Frenchmen who live in Paris. It isn’t that the French don’t have any duties in justice to Italians. Rather, it is that they have particular responsibilities to their fellow French citizens that they don’t have to Italians—and vice versa.

There is, however, another dimension to national sovereignty that complements the existence of these common bonds and sympathies. This is illustrated by way of analogy—one made by thinkers ranging from John Rawls to Rocco Buttiglione and John Finnis—with some of the arguments for private property developed by figures such as Aristotle and Aquinas. As Buttiglione writes, “The public equivalent of private property is sovereignty.”

National Boundaries and the Analogy of Property

One argument for private property’s legitimacy is that experience shows that the resources with which all of humanity has been endowed are normally made more fruitful when divided and possessed by individuals rather than owned in common. The indisputable economic degradation associated with socialist regimes underscores the truth of this observation. Likewise, the international order is better organized when the world is divided into sovereign states made up of peoples who share those common bonds that facilitate order within a territory recognized as their own.

There’s no indication at present or in the foreseeable future that the conditions exist that would allow some type of world authority to assume responsibility for maintaining order for humanity as a whole. Few Poles, Israelis, or Chinese would, for example, voluntarily risk their lives for the United Nations. Yet does anyone doubt that millions of Poles, Israelis, and Chinese would be willing to defend Poland, Israel, and China respectively?

Similarly, serious threats to international order are invariably addressed by nation-states rather than international organizations. It was Britain, America, and other countries that had to end the danger posed to humanity by National Socialist Germany’s racist and expansionist policies. The League of Nations proved ineffectual at doing so. Similarly, it wasn’t the United Nations that defeated the threat to civilization created by the Soviet Union and its Marxist-Leninist ideology. A sovereign nation-state had to take the lead: the United States.

Private property’s ability to achieve its end of ordering the use of the world’s resources by all is, however, heavily dependent on each owner’s (1) liberty to exclude others from using his property and (2) freedom to decide how he wants to use his property, subject to the restraints of just laws. Without these powers, private property is effectively nullified, and we are plunged into the tragedy of the commons.

So too with national sovereignty. A nation of twenty million people may rightly decline to admit ten million migrants who suddenly appear at its borders on the reasonable grounds that admitting all these migrants would severely disturb the nation’s internal harmony. Likewise, if a country doesn’t possess the freedom to exclude those potential migrants whose beliefs and actions threaten the nation’s well-being—such as those with no intention of abiding by its just laws, or those who disdain, reject, or want to destroy that nation’s patrimony—then the order and stability that sovereignty protects is undermined. This is why a sovereign state may apply conditions of residence to non-citizens that are not applicable to citizens, refuse to admit non-citizens, or choose to expel non-citizens (subject to due process of law).

It may well be that a sovereign state determines that its well-being may be enhanced, for example, by an increase in population occasioned by immigration, or the entry of migrants with particular skills, or the admission of large numbers of migrants who simply want to work and pursue economic opportunities less available to them in their native lands. In many cases, such policies have contributed to the prosperity and common good of nations.

Recognizing a sovereign state’s authority to make such policies is, however, entirely different from claiming that a sovereign state must admit, as a matter of right, any non-citizen who presents himself at its borders and demands entry, no questions asked. No such right can be derived from the criteria listed above.

And Immigration?

So what are the implications of this conception of national sovereignty for migration? Again, the analogy with private property is helpful.

In cases of extreme necessity—which, Aquinas specifies, means “a person is in some imminent danger, and there is no other possible remedy” (rather strict criteria)—private property becomes common to the extent that this will meet the immediate need. Applying this logic to the case of migration, we can say that those facing imminent danger because of conditions such as war, persecution, or famine in their country and who don’t possess any other remedy for their plight can rightly seek refuge in another nation.

This indicates that a sovereign state’s power to exclude non-citizens isn’t absolute. But it doesn’t mean that a given sovereign state is duty-bound to admit any migrant who simply asserts he confronts imminent danger if he remains in his native land. Nor does it imply that genuine refugees can insist on asylum in whatever country they happen to choose. No one who migrates to escape imminent danger can claim that his or her need for refuge can only be fulfilled by, say, the United States and not by any other nation whatsoever.

Fulfilment of their duties to (1) those who really do face imminent danger and (2) their own citizens means that sovereign states have the responsibility to determine whether such migrants would indeed be in imminent danger if they stayed in their native land. At the same time, a sovereign state has an obligation to its citizens to insist that those migrants identified as being in such danger will obey all its just laws and won’t constitute a threat to public order or undermine the nation’s common good.

Clearly, it’s difficult to estimate accurately the number of genuine refugees or those seeking to migrate to another country in the world today. But what isn’t in doubt is that the ongoing difficulties associated with widespread population movements between sovereign nation-states aren’t resolvable in a just way through endless assertions of an unspecified right to migrate. Unless legislators and citizens come to a greater understanding of the order created by national sovereignty and its contribution to the common good of both individual nations and the international community, our present-day divisions about immigration will only intensify.