Regional disparities in immigration enforcement have existed for decades, yet they remain largely overlooked in immigration law scholarship. This Article theorizes that bottom-up pressure from states and localities, combined with top-down pressures and policies established by the President, produce these regional disparities. The Article then provides an empirical analysis demonstrating enormous variations in how Immigration and Customs Enforcement’s twenty-four field offices engage in federal enforcement around the United States. By analyzing data related to detainers, arrests, removals, and detention across these field offices, the Article demonstrates substantial differences between field offices located in sanctuary and anti-sanctuary regions, as well as variations within each of those groups. In order to promote more equitable and transparent enforcement, the Article offers recommendations regarding agency guidelines, rulemaking, performance metrics, and institutional designs, examining the strengths and limitations of these approaches.