Since the mid-1990s, academic studies of US immigration history have undergone a “sea change” (xxi). This book was influenced by that sea change and contributed to it. By demonstrating that national boundaries have always been porous and migration patterns diverse, the interdisciplinary field of migration studies has led to changes in academic approaches. Historians have replaced the old studies of one-way migration, permanent settlement, inclusion, and assimilation with studies of transnationalism, diasporas, borderlands, and colonialism. Transnational studies emphasize the political and cultural influences on sending and receiving nations, while studies of diasporas compare migrant experiences across the world.

While the old assimilationist paradigm minimized racial questions, new studies have emphasized the importance of racialized identities for Asians, Latino/as, and Europeans. These new trends are apparent in this book via “its analysis of the production of racial knowledge and national identity, the construction of the border, and the influence of colonialism on migration policy” (xxiii). However, the book focuses on US law and enforcement and migrant experiences within the country.

Illegal immigrants are excluded from the national community, yet are a part of communities and work forces in the US. As such, they are “impossible subjects” (xxiv)—a social reality but legal impossibility.