Joseph Carens argues persuasively that some undocumented immigrants should be able to adjust to lawful status and eventually obtain citizenship by virtue of time spent within the host country. Where undocumented immigrants have strong enough social connections in their adopted states and have otherwise become productive members of society, the “harm” from enforcement (i.e., forced deportation) is “entirely out of proportion to the wrong of illegal entry.” Carens also recognizes, without emphasizing it, that the opposite point also follows: for immigrants with very weak connections, the benefits of enforcement outweigh the migrants’ moral claims to remain. Thus, the policy question is all about where to draw this line.

I have three disagreements with Carens on how to distinguish between deserving and undeserving cases. First, Carens argues that the overwhelmingly important issue is the amount of time an undocumented immigrant has spent in the United States, and he warns against “subjectively” weighing other mitigating factors like family and community connections in the United States. Yet to ignore these factors also represents a value judgment, and in fact the citizen families (and employers) of undocumented immigrants are among the biggest losers from an enforcement-only policy. The distribution of scarce visas (or scarce opportunities for legalization) must account for the claims of these citizens.

Second, Carens argues against attaching a penalty to legalization (i.e., he favors “amnesty” over “earned legalization”) on the grounds that illegal migration is not a serious crime. But his own analogy implies the opposite conclusion: if undocumented immigrants are similar to speeders, then requiring them to pay a fee or to perform community service is an appropriate part of the legalization process. A speeder should not have her car taken away for a first violation, but there is no moral claim against paying a speeding ticket. The legalization process also must be burdensome so as not to encourage future undocumented immigrants—a consideration Carens is too quick to discount after our experience with the Immigration Reform and Control Act’s permissive legalization regime—and to satisfy Americans’ broader sense that misdeeds (such as jumping the queue for legal visas) should be punished.

Third, if Carens is too forgiving of immigrants’ culpability in arguing for a penalty-free amnesty, he is also too lenient toward U.S. policies and their promotion of illegal inflows. On a basic level, U.S. policy decisions “constructed” illegality in the first place by imposing a visa regime on an existing social and economic phenomenon. But the more important point is that the underlying structure of migration flows—the pushes, pulls, and social networks that overwhelm visa restrictions—are themselves the product of policy choices. In the case of the United States and Mexico, for example, active U.S. recruitment of “guest workers” after World War II initiated the modern migration system; and the failure to include labor provisions in the NAFTA agreement and other trade deals sustains migration pressure.

The harm of an enforcement-only approach to the U.S. citizens connected to undocumented immigrants, and the role of policy decisions in creating the problem both suggest that a more inclusive approach to earned legalization (but not amnesty) is required. Why, then, does comprehensive immigration reform remain so controversial?

One set of reasons, surely, is ideological. Some Americans place more weight on the tradition of personal responsibility than the equally American concepts of forgiveness and rehabilitation. A more troubling form of ideology is rooted in racial and ethnic bias, as some Americans apply different standards to immigrants of color and migrants from the developing world than they do to European migrants, whether recent or from earlier waves of migration.

Yet even if we agree on the morality of earned legalization, designing a successful and fair policy of earned legalization is still a challenge. In particular, how can a penalty structure satisfy our sense of justice and deter future undocumented flows while still accomplishing its primary goal of allowing meritorious immigrants to take advantage of the program and to become full members of U.S. society? The scope of the problem is also daunting, especially because undocumented immigrants will rightly be required to “get at the back of the line” behind would-be legal immigrants with pending visa applications—a group of some 4.9 million for whom visas are not currently available. Thus, legalization inevitably implies significant growth in the United States’s legal migration system, at least in the short-run, which is an especially hard sell in the midst of a historic recession.

The logic of Carens’s argument also suggests a framework for resolving this tension moving forward. The United States should consider replacing most non-family and non-humanitarian migration—including the majority of existing “temporary workers,” but also perhaps most recipients of employment-based and “diversity” green cards—with “provisional” visas. These visas would grant temporary work eligibility and would allow immigrants to transition into more complete levels of membership as they accrue a greater moral claim to permanent residence (based on time in the United States) and as they demonstrate their ability to contribute to the U.S. economy and society (based on a documented history of legal work, payment of taxes, English language acquisition, etc.). The terms of the provisional visa could be set, by definition, to guarantee that immigrants who qualify for a “contract extension” meet the criteria seen as desirable in future citizens.

By opting into this system, immigrants also would agree to make the contracts enforceable, perhaps by accepting additional reporting requirements during the early period of their visas; and they would give up a moral claim to remain in the United States if they fail to meet the requirements of the provisional visa. A system like this would lower the stakes of more generous visa numbers up front because it would recognize that not all immigrants want to be or should be on a path to permanent residency or citizenship. But it would also build in the flexibility to insure that those who remain do so legally and by mutual consent.