This article examines how changing legal institutions have structured workers' collective decision to strike. It uses both qualitative legal-historical analysis and quantitative time-series regression to examine how major changes in labor law in the late 1930s altered workers' willingness and opportunity to strike. Previous research has assumed that important change in workplace relations occurred in the late 1940s. The present work relocates that change to the late 1930s with a number of important implications. In particular, this study shows that the federal government, both its legislative and judicial branches, was an important shaper of workplace relations. State legal policy regulating labor militancy prior to the late 1930s is labeled “repressive intervention” while the state's intervention after the New Deal is defined as “integrative prevention.”