Countless observers, from the Framers to modern day academics, examine the government's capacity to enact new legislation. Congress in Reverse is the first book to focus on repeals as an important and distinct legislative action. It examines two primary questions. First, are law creation and law repeal are governed by the same dynamics? As a technical matter, the constitutional and institutional constraints are the same, so perhaps a repeal is “just another law.” Despite this, Ragusa and Birkhead show that repeals face a unique set of constraints and are therefore harder to pass than any other type of legislation, including amendments, reauthorizations, and new laws. Further, the data reveal that productive congresses do not automatically repeal a large volume of statutes and that the usual determinants of law creation are poor predictors of repeal occurrence. Second, which of the leading theories of lawmaking—problem solving, parties, or preferences—best explain when and why repeals occur? Although all three help make sense of repeals, Ragusa and Birkhead develop an explicit theory that focuses on the majority party’s cohesiveness its recent experience out of power. Ultimately, the data show that repeals are most likely to succeed when the majority is ideologically cohesive and recently won power after a long time in the minority. In this respect, while most lawmaking follows exogenous policy problems and takes place on a bipartisan basis, when Congress tries to undo landmark legislation—such as the Affordable Care Act—it tends to do so for partisan reasons.