Selection forces often confound the effects of policy changes. In the immigration enforcement context, we tackle this challenge tracking arrested immigrants along the deportation pipeline, isolating local and federal efforts. 80% of counties exhibit strategic substitutabilities in responding to federal enforcement, while the federal level is very effective at directing its efforts toward cooperative counties. We estimate that changes in the profile of immigration cases, and not weakened federal efforts, drove the reduction in deportations following a 2011 shift in federal priorities. Reducing immigration-court discretion and removing their dependence from the executive would have a significant impact on deportations.