The United States' southern border with Mexico runs for approximately 2,000 miles over diverse terrain, varied population densities, and discontinuous sections of public, private, and tribal land ownership. The Department of Homeland Security (DHS) Customs and Border Protection (CBP) is primarily responsible for border security, including the construction and maintenance of tactical infrastructure, installation and monitoring of surveillance technology, and the deployment of border patrol agents to prevent unlawful entries of people and contraband into the United States (including unauthorized migrants, terrorists, firearms, narcotics, etc.). CBP's border management and control responsibilities also include facilitating legitimate travel and commerce.
Existing statute pertaining to border security confers broad authority to DHS to construct barriers along the U.S. border to deter unlawful crossings, and more specifically directs DHS to deploy fencing along "at least 700 miles" of the southern border with Mexico. The primary statute is the Illegal Immigration and Immigrant Responsibility ACT (IIRIRA) as amended by the REAL ID Act of 2005, the Secure Fence Act of 2006, and the Consolidated Appropriations Act of 2008.
On January 25, 2017, President Trump issued Executive Order 13767 "Border Security and Immigration Enforcement Improvements," which addresses, in part, the physical security of the southern border and instructed the DHS Secretary to "take all appropriate steps to immediately plan, design, and construct a physical wall along the southern border, using appropriate materials and technology to most effectively achieve complete operational control." The order did not identify the expected mileage of barriers to be constructed.
The three main dimensions of border security are tactical infrastructure, surveillance technology, and personnel.
Tactical Infrastructure. Physical barriers between ports of entry (POE) on the southern border vary in age, purpose, form, and location. GAO reports that at the end of FY2015, about one-third of the southern border, or 654 miles, had a primary layer of fencing: approximately 350 miles designed to keep out pedestrians, and 300 miles to prevent vehicles from entering. Approximately 90% of the 654 miles of primary fencing is located in the five contiguous Border Patrol sectors located in California, Arizona, and New Mexico, while the remaining 10% is in the four eastern sectors (largely in Texas) where the Rio Grande River delineates most of the border. About 82% of primary pedestrian fencing and 75% of primary vehicle fencing are considered "modern" and were constructed between 2006 and 2011. Across 37 discontinuous miles, the primary layer is backed by a secondary layer (pedestrian) as well as an additional 14 miles of tertiary fencing (typically to delineate property lines). No new miles of primary fencing have been constructed since the 654 miles were completed in 2015, but sections of legacy fencing and breached areas have been replaced. Additional tactical infrastructure includes roads, gates, bridges, and lighting designed to support border enforcement, and to disrupt and impede illicit activity.
Surveillance Technology. To assist in the detection, identification, and apprehension of individuals illegally entering the United States between POEs, CBP also maintains border surveillance technology. Ground technology includes sensors, cameras, and radar tailored to fit specific terrain and population densities. Aerial and marine surveillance vessels, manned and unmanned, patrol inaccessible regions.
Personnel. Approximately 19,500 Border Patrol agents were stationed nationwide, with most (16,600) at the southern border in FY2017. Subject to available appropriations, Executive Order 13767 calls on CBP to take appropriate action to hire an additional 5,000 Border Patrol agents. However, CBP continues to face challenges attaining statutorily established minimum staffing levels for its Border Patrol positions despite increased recruitment and retention efforts.
Southern border security may be improved by changes to tactical infrastructure, surveillance technology, and personnel. A challenge facing policymakers is in determining the optimal mix of border security strategies given the difficulty of measuring the effectiveness of current efforts. While the number of apprehensions of illegal entrants has long been used to measure U.S. Border Patrol performance, it does not measure illegal border crossers who evade detection by the Border Patrol. When apprehensions decline, whether it is due to fewer illegal entrants getting caught or fewer attempting to enter illegally is not known. Other difficulties include measuring the contribution of any single border security component in isolation from the others, assessing the extent to which enforcement actions deter illegal crossing attempts, and evaluating ongoing enforcement efforts outside of border-specific actions and their impact on border security.
Section 1092 of the FY2017 National Defense Authorization Act (NDAA) directs the Secretary of Homeland Security to provide annual metrics on border security that are intended to help address some of the challenges of measuring the impact of border security efforts. DHS has produced baseline estimates that go beyond apprehensions statistics to measure progress towards meeting the goals contained in Executive Order 13767.
Congress, through CBP appropriations—and appropriations to its predecessor agency, the Immigration and Naturalization Service (INS)—has invested in tactical infrastructure, surveillance technology, and personnel since the 1980s. Given the changing level of detail and structure of appropriations for border infrastructure over time, it is not possible to develop a consistent history of congressional appropriations specifically for border infrastructure. However, CBP has provided the Congressional Research Service (CRS) with some historical information on how it has allocated funding for border barrier planning, construction, and operations and support. Between FY2007 and FY2018, CBP allocated just over $5.0 billion to these activities, including almost $1.4 billion specifically for border barrier construction and improvement through a new "Wall Program" activity in its FY2018 budget.
The 116th Congress is considering a mix of tactical infrastructure, including fencing, surveillance technologies, and personnel to enhance border security between U.S. POEs. Some experts have warned that the northern border may need more resources and oversight than it is currently receiving in light of potential national security risks. Other border security priorities that may be considered during the 116th Congress include improvements to existing facilities and screening and detection capacity at U.S. POEs.