"About 362 million travelers (citizens and non-citizens) entered the United States in FY2013, including about 102 million air passengers and crew, 18 million sea passengers and crew, and 242 million land travelers. […] CBP's primary immigration enforcement mission at ports of entry is to confirm that travelers are eligible to enter the United States and to exclude inadmissible aliens. Yet strict enforcement is in tension with a second core mission: to facilitate the flow of lawful travelers, who are the vast majority of persons seeking admission. A fundamental question for Congress and DHS is how to balance these competing concerns. In general, DHS and CBP rely on 'risk management' to strike this balance.[…] DHS also is responsible for implementing an electronic entry-exit system at POEs. Congress required DHS' predecessor to develop an entry-exit system beginning in 1996, but the implementation of a fully automated, biometric system has proven to be an elusive goal. […] The inspections process and entry-exit system continued to be perennial issues for Congress and a number of questions persist, including in the context of the ongoing debate about immigration reform and in the context of screening for infectious diseases at POEs due to heightened concerns about the health screening of people arriving in the United States from the Ebola infected areas in West Africa. What is the scope of illegal migration through ports of entry, and how can Congress and DHS minimize illegal flows without unduly slowing legal travel?"
CRS Report for Congress, R43356