This article addresses two questions: First, what explains the very low level of ratifications of the international legal instruments for the protection of the rights of migrant workers? Second, what are the implications for research and policy debates on the rights of migrant workers in practice? The author argues that the key reason for the underratification and limited effectiveness of international migrant rights conventions relates to the perceived and/or real consequences (different types of costs and benefits) of extending rights to migrants for the national interests (however defined) of nation-states. In addition to their intrinsic value, the rights of migrant workers play an important instrumental role in shaping the outcomes of international labor migration for receiving countries, migrants, and their countries of origin. Migrant rights are in practice a core component of nation-states’ labor immigration policies, which involve decisions on the number and type of migrants to be admitted as well as their rights after admission. Consequently, migrant rights cannot be studied in isolation of admission policy, in terms of both positive and normative analysis. To understand why, when, and how countries restrict migrant workers’ rights, and to discuss what rights migrant workers should have, one needs to consider the potential interrelationships between migrant rights, on one hand, and national policies for admitting migrant workers, on the other hand. This opens up a new and important research agenda that has thus far remained largely unexplored.