Modern states claim the right to decide who can enter their territory. Joseph Carens here grants this claim: he assumes that states have a right to control their borders. Still, he argues that liberal democratic states have a moral duty to grant residency status to extra-legal migrants if they have lived in the territory for a sufficiently long period of time. My thesis is this: if moral duties to noncitizens inside a state’s borders limit the state’s right to control its borders, then moral duties to noncitizens outside its borders also limit this right. If Carens’s argument is successful (and I think it is), it pulls the rug out from under his starting point: the state does not have absolute moral discretion over whom it excludes in the first place.

Carens argues that when human beings reside in a society for a length of time, they incur a vast array of social ties comprising “their deepest human connections”: they develop friendships, family, and emotional attachments; even their personalities are molded by the society. These social ties are morally significant because they comprise a “fundamental human interest.” They impose a moral duty on the state because they are so vulnerable to the state’s exercise of power. Thus Carens seems to apply the following principle: if someone’s fundamental interests are vulnerable to the exercise of state power, then the state is morally obliged to take those interests into account in how it exercises power over her, even if the person is a noncitizen.

Here lies the rub: existing social ties, no matter how deep, are not the only fundamental human interests. The migrant experience makes the point painfully obvious. Migrants frequently leave behind all their existing social ties. Why would anyone do this? Sometimes, because an even more fundamental interest is immediately at stake: life, limb, liberty. Sometimes, the dream of a better life. Indeed, social ties are often important precisely because they are constituents of a person’s life projects, or the necessary means for realizing them. Our existing social ties are not our only, and sometimes not even our most, fundamental interests.

Consider the case of Niloufar Folani. All of her family and friends live in Iran, and she has been socialized there for the first 21 years of her life. Yet, as a woman, her legal protections against violence by men are precarious. And, as a Bahá’í, she cannot freely practice her religion or attend university. Under the country’s constitution, she is a legal nonperson. She has learned French, and wishes to migrate to Quebec, in search of personal security, education, and religious freedom. Her fundamental interests are at stake, more fundamental to her than her existing social ties. If the state is obliged by fundamental human interests, regardless of citizenship, then what distinguishes Folani from Miguel Sanchez, the extra-legal migrant discussed by Carens? Why should the United States offer residency to Sanchez but Canada refuse Folani?

Some may argue that the difference is that Sanchez is in some sense already a member of U.S. society and that this social membership is what imposes a moral duty on the state. But this is not Carens’s argument, and rightly so. For Carens, Sanchez’s presence in U.S. territory, over a period of time, is significant only because it is a reliable sign that his fundamental interests are at stake. Sanchez’s “social membership“ is significant because it implies that his fundamental interests are vulnerable to the state’s regime of border control. But someone outside the state, whose fundamental interests depend on immigrating, is equally vulnerable to that regime. When the state enforces its border laws, not only citizens and residents, but also nonresident foreigners are subject to its exercise of coercive power.

That leaves only two options. Either the state is sometimes obliged by the interests of noncitizens—whether it may justly exclude a foreigner depends on what kind of interests are at stake. Or, the state is only morally obliged by the interests of its own citizens, and it may justly exclude foreigners from its territory how it sees fit. It may ignore the interests of territorial outsiders; it may ignore Sanchez’s interests too.

Only the first option is consistent with liberal democracy. Defenders of absolute state sovereignty traditionally argued that the state’s exercise of power is legitimated by its capacity to keep the peace and protect from attack. By virtue of this capacity, the state was the sovereign arbiter of how political power may be exercised. But the whole point of liberal democracy is that the state’s legitimate exercise of power is limited by moral constraints. A state is liberal insofar as it respects the rights and interests of the human beings on whom it imposes its might. It is democratic insofar as it ultimately attributes sovereignty to the people, not to itself.

By recognizing their own populations as rights-bearing citizens, liberal democratic states have, to some extent, institutionalized these constraints. But it is insufficient for the state to respect only the fundamental interests of people it recognizes as citizens. If the state subjects blacks or women to its coercive power, without respecting their fundamental interests, it cannot save its legitimacy by refusing to recognize them as full citizens. Liberal democracy aspires to be government of, by, and for the people. Which people? The very people whom the state subjects to its laws and power, not just those whom the state has agreed to call citizens.

Border laws pose a unique problem because they inherently subject both citizens and foreigners to the state’s exercise of power. This is why a liberal democracy does not legitimately enjoy absolute discretion to determine its own border laws: for the same reason that it does not have absolute discretion in how it treats its own domestic population.

To advocate policy proposals with a realistic chance of adoption, one must sometimes take for granted society’s most entrenched ideological assumptions. These assumptions delimit the politically feasible at a given moment. Yet even in granting the state’s sovereignty over its borders, Carens’s proposal on behalf of extra-legal migrants like Sanchez is bold. As a matter of political strategy, it is the right policy to advocate, particularly in the U.S. context. But Carens’s argument offers a deeper challenge to those who read carefully: it surreptitiously undermines the false ideological premise it began by seemingly granting.