Joseph Carens describes several individual cases that are poignant and worthy of remedy. But exactly why the United States—its Congress or people—have a moral obligation to assist undocumented migrants is under-argued. Carens refers to a number of possible lines of analysis but never settles on a particular argument; he is letting the obvious inhumanity of the treatment of Miguel Sanchez, Margaret Grimmond, and Hiu Lui Ng do the work for him. It is “morally wrong,” we are told,

to force someone to leave the place where she was raised, where she received her social formation, and where she has her most important human connections, just because her parents brought her there without official authorization.

What justifies this intuition?

Carens offers several arguments. First, he makes a claim from membership. That can be worked out in two ways. The first focuses on social facts: long-term undocumented migrants have made the United States their home; indeed, for those who arrived as children (the so-called 1.5 generation), they really may know no other home. They belong, in two senses of the word: they belong in the United States and they belong to American society. Deportation strips long-term residents of this membership, separating them from family and community. If these are the kinds of ties that make life meaningful and pleasurable, that help us flourish as human beings, then there is a moral argument against policies that undermine them.

The claim from membership also has an equal-protection dimension. If long-term undocumented residents are, in effect, members, and if we do not deport citizens, then to remove some members but not other, similarly situated members would be arbitrary. This kind of argument held sway in the 1982 case Plyler v. Doe, in which the Supreme Court found unconstitutional a Texas statute barring undocumented children from public schools. According to the majority opinion, these children would in all likelihood become members of our society; to deny them education would create, in effect, a caste of second-class members.

A second argument Carens employs is a claim from family. As Carens notes, family life is deemed a fundamental human right. Article 16 of the Universal Declaration of Human Rights states: “The family is the natural and fundamental group unit of society and is entitled to protection by society and the State.” To deport a long-term undocumented resident is likely to severely undermine the exercise of that right in the United States. This argument has received some play under European human rights instruments, but it has not carried weight in the United States. Adjudicators have worried about the incentives it creates for undocumented migration. Furthermore, deportation does not destroy family unity; it may simply require it to take place in another country.

Carens’s third line of argument is a claim from proportionality. He writes that to “uproot a person who has spent fifteen or twenty years as a contributing member of society” would be “cruel and inhumane”: “The harm is entirely out of proportion to the wrong of illegal entry.” This appears to be an extension, or restatement, of the claim from membership. In any event, how one quantifies the “wrong of illegal entry” is not further elaborated upon, nor is the concept of proportionality linked to a deeper moral theory.

I am not sure which of these arguments Carens thinks carries the day—or perhaps his view is that all of them add up to a strong moral claim. They may well. But without full development of the underlying moral theories it is difficult to know.

Making the case for relief from removal on somewhat more prosaic policy grounds may be more fruitful. It is common for countries’ immigration laws to provide avenues—written into statute or established through the exercise of administrative discretion—for unauthorized migrants to remain when the harm to them, their family, and the community significantly outweighs the harm of illegal entry and where there are no other strong grounds warranting removal (such as the commission of a serious criminal offense). As Carens notes, U.S. law has for some time included a statute that permits case-by-case determinations of this kind; the law was unduly tightened in 1996, when Congress added the requirement that undocumented migrants seeking relief from removal demonstrate that their removal would result in “exceptional and extremely unusual hardship” to a close family member who is a U.S. citizen or green-card holder.

Carens seeks more than discretionary intervention, arguing for a rolling statute of limitations available to undocumented migrants who have spent a significant length of time in the United States. Such a rule is likely to be over-inclusive and under-inclusive, but this lack of fit may be justified on administrative grounds—again as a matter of policy. An even broader form of relief is possible, and it has received the greatest attention in recent immigration debates: legalization for undocumented migrants, even those who have been here a relatively short period of time, provided they pay a fine, learn English, have paid their taxes, and have not committed a serious crime.

For all these proposals, moral claims can be made on both sides. The social facts of undocumented life may be said to create a kind of membership that has moral weight, but there is also the moral claim of a self-governing people to determine who should be members of their polity—a claim that might not diminish in significance simply because an unlawful entrant has evaded detection for some length of time (the dissenting justices in Plyler made precisely this point: the presence of the undocumented children in Texas schools had never been consented to by “We the People” or our elected officials). Or the moral claim from proportionality that argues for relief from removal can be compared to the moral claim of those who wait patiently in line outside the United States—some for many years; people who, had they entered illegally, could have established the kind of ties in the United States that are now said to justify legal status for the queue jumpers. Indeed, I worry that the attempt to make the argument on moral grounds could jeopardize the chance for a solution that would aid the persons Carens cares about, as opponents line up moral claims on the other side.

Pragmatic arguments may, in the end, be the most persuasive. For the long-term undocumented residents about whom Carens writes, Congress ought to return the law to its pre-1996 form. Congress should also adopt a general legalization program: the U.S. government simply is not going to send home eleven million undocumented residents—the costs of enforcement would be too high, the clamor from communities would be too great—whether or not the American people recognize a powerful moral claim that they be permitted to remain. Legalization has its costs in terms of providing incentives to enter illegally and expanding eligibility for social programs. But on balance these costs are likely to be outweighed by the benefits of protecting against exploitation and promoting integration into American society.