To understand border enforcement and the shape it has taken, it is imperative to examine a groundbreaking Border Patrol operation begun in 1993 in El Paso, Texas, "Operation Blockade." The El Paso Border Patrol designed and implemented this radical new strategy, posting 400 agents directly on the banks of the Rio Grande in highly visible positions to deter unauthorized border crossings into the urban areas of El Paso from neighboring Ciudad Juarez--a marked departure from the traditional strategy of apprehending unauthorized crossers after entry. This approach, of "prevention through...