This article introduces the law‐before as an analytic tool for enhancing explanations of legal reform. Based on an integration of neo‐institutional law and organizations studies and punishment studies of local variation in penal policy, I define the law‐before as the past organizational practices and power arrangements that precede law‐on‐the‐books and shape present day implementation. I utilize the law‐before as a heuristic to investigate the legacy effects of variations in local practice on the implementation of the prison downsizing law, AB 109, or “Realignment,” in California. I analyze organizational documents produced by county practitioners in the aftermath of AB 109's enactment in 2011 as empirical windows into how actors shape the meaning of law in local settings. I find that practitioners in counties with divergent historical imprisonment patterns enact four processes (overwriting or underwriting law, selective magnification, and selective siting) to arrive at distinct interpretations of AB 109 as mandating system‐wide decarceration or the relocation of incarceration from state prisons to county jails. Although my data do not speak to the ultimate implementation of AB 109, the processes revealed have practical implications for the reform goal of decarceration by rationalizing distinct resource allocations at an early stage in the implementation process.