This dissertation reconstructs Ashkenazi and Sephardi German Jews’ intensive pursuit of civil and religious rights before Germany’s Imperial Supreme Court (Reichskammergericht, the Imperial Chamber Court) in the context of the wide-ranging religious and legal reforms in the sixteenth and seventeenth centuries. Through my systematic analysis of 75,000 court records and my examinations of manuscripts and early printed materials from more than thirty archives across three continents, I study hundreds of previously untapped Supreme Court cases alongside religious and legal sources in German, Hebrew, Yiddish, Spanish, Portuguese, and Latin. I take an integrative approach to this wealth of sources to argue that by using the Supreme Court in numbers that far exceeded their proportion of the population, including in matters that pertained to Jewish law, this litigious minority generated grounds for inter-religious exchanges with the court’s Christian lawyers and judges. These lawyers endeavored to understand and incorporate Jewish law into imperial procedure, not merely due to their commitment to conflict resolution, but also due to their interest in advancing the universal applicability of Roman law as a sophisticated tool to conjoin the different limbs of the empire into a cohesive state. These efforts led the Supreme Court, and therefore the state, to protect rabbinic law and secure the continuation of a Jewish presence in Germany, thus moving in an opposite direction from key religious reformers and local authorities. This dissertation reveals that the study of Jews’ surprising strategies of interconnecting law and religion in defense of themselves and their religious laws promoted Jews’ civil rights in radical ways, and attained a de facto status of imperial citizenship for Ashkenazi and Sephardi-Portuguese Jews. Unearthing knowledge from the archives, this dissertation redraws the porous boundaries between Jewish and non-Jewish legal cultures and calls for a reconsideration of early modes of Jewish citizenship. Showing how Jewish women and men, including Iberian refugees, employed litigation as an anti-nomadic tool against pending expulsions, this dissertation also challenges prevalent conventions on weak Jewish responses to persecution, forced migration, and the agency that ethnic and religious minorities can wield in state-building processes.