Border enforcement is a core element of the Department of Homeland Security's (DHS's) effort to control illegal migration, with the U.S. Border Patrol (USBP) within the Bureau of Customs and Border Protection (CBP) as the lead agency along most of the border. Border enforcement has been an ongoing subject of congressional interest since the 1970s, when illegal immigration to the United States first registered as a serious national problem; and border security has received additional attention in the decade following the terrorist attacks of 2001.

Border enforcement is a core element of the Department of Homeland Security's (DHS's) effort to control unauthorized migration, with the U.S. Border Patrol (USBP) within the Bureau of Customs and Border Protection (CBP) as the lead agency along most of the border. Border enforcement has been an ongoing subject of congressional interest since the 1970s, when illegal immigration to the United States first registered as a serious national problem; and border security has received additional attention in the years since the terrorist attacks of 2001. Since the 1990s, migration control at the border has been guided by a strategy of "prevention through deterrence"-the idea that the concentration of personnel, infrastructure, and surveillance technology along heavily trafficked regions of the border will discourage unauthorized aliens from attempting to enter the United States. Since 2005, CBP has attempted to discourage repeat entries and disrupt migrant smuggling networks by imposing tougher penalties against certain unauthorized aliens, a set of policies eventually described as "enforcement with consequences." Most people apprehended at the Southwest border are now subject to "high consequence" enforcement outcomes.

The United States confronts a wide array of threats at U.S. borders, ranging from terrorists who may have weapons of mass destruction, to transnational criminals smuggling drugs or counterfeit goods, to unauthorized migrants intending to live and work in the United States. Given this diversity of threats, how may Congress and the Department of Homeland Security (DHS) set border security priorities and allocate scarce enforcement resources? In general, DHS's answer to this question is organized around risk management, a process that involves risk assessment and the allocation of resources based on a cost-benefit analysis. This report focuses on the first part of this process by identifying border threats and describing a framework for understanding risks at U.S. borders. DHS employs models to classify threats as relatively high- or low-risk for certain planning and budgeting exercises and to implement certain border security programs. Members of Congress may wish to use similar models to evaluate the costs and benefits of potential border security policies and to allocate border enforcement resources. This report discusses some of the issues involved in modeling border-related threats. Understanding border risks begins with identifying key threats. At their roots, border-related threats are closely linked to the flow of people (travelers) and goods (cargo) from one country to another. Any smuggled item or individual hidden among the legitimate flows potentially constitutes a threat to U.S. security or interests. The intentions and actions of unauthorized travelers separate them into different threat categories, including terrorists, transnational criminals, and other illegal migrants.

History and geography have given Mexico a unique status in the U.S. immigration system, and have made the Mexico-U.S. migration flow the largest in the world. Mexicans are the largest group of U.S. migrants across most types of immigration statuses-a fact that may have important implications for how Congress makes U.S. immigration policy. This report reviews the history of immigration policy and migration flows between the countries and the demographics of Mexicans within the United States. It also analyzes contemporary issues in U.S. immigration policy and the impact Mexico may have on U.S. immigration outcomes.

In The Oxford Handbook of the Politics of International Migration, leading migration experts Marc Rosenblum and Daniel Tichenor gather together 29 field specialists in an authoritative volume on the issue. Integrating the perspectives of the wide variety of fields that hold a stake in the study of migration-political science, sociology, economics, anthropology-this book presents an unprecedented interdisciplinary look at an issue that defines the modern era: the large-scale movement of people across international borders. The volume begins with three chapters analyzing the origins and causes of migration, including both source and destination states. The second section then asks: what are the consequences of migration at both ends of the migration chain? Chapters in this section consider economics, the effects of migration on parties and political participation, and social and cultural effects. A third group of chapters focuses on immigration policy. These include primers on the history and dimensions of migration policy, as well as examinations of the effects of public opinion, interest groups, and international relations on policymaking. The volume then considers aspects of the immigrant experience: segmented assimilation among Asian Americans, histories of U.S. immigrant incorporation and of race and migration, transnationalism, and gendered aspects of migration. Finally, five chapters examine contemporary issues, including transborder crime and terrorism, migration and organized labor, international regionalism, normative debates about citizenship and immigration, and the recent history of U.S. immigration policymaking. Covering the major questions and challenges related to the issue, The Oxford Handbook of the Politics of International Migration is a comprehensive resource for students, scholars, and policy experts alike.