Immigrant legalization policies pose an ethical dilemma for liberal democracies. On the one hand, liberal democracies aspire to respect the basic equality of all persons. Compelling moral arguments have been made for granting legal status and a path to citizenship to unauthorized migrants by virtue of the social ties that they have developed, their contributions to the host society, and their vulnerability to exploitation and subordination. On the other hand, legalization poses a challenge to another important value, the rule of law, which requires government to operate within a framework of law in accordance with well-established public norms, not in an arbitrary or ad hoc manner. Immigrant legalization programs are said to undermine the rule of law because they reward lawbreaking, allow queue-jumping, and incentivize further unauthorized migration. This article clarifies each horn of the dilemma, focusing on rule of law arguments since less has been written about them. We assess both the empirical assumptions and normative interpretations embedded in rule of law arguments. We concentrate on the United States but also give some attention to legalization in other countries. We acknowledge that some of the rule of law objections to legalization have merit, but we argue that there are also rule of law arguments that support legalization, which help to mitigate, although not eliminate, the dilemma. We conclude by discussing the implications of our analysis and considering how liberal democratic states might better manage the dilemma.