Recent scholarship on Jews in the medieval Islamic world has upended ideas about dhimmī “communal autonomy” that held sway for much of the twentieth century, emphasizing instead that Jews of all social strata participated extensively in the political culture of the Islamic states under which they lived: communal leaders and non-elites alike maintained patronage relationships with Islamic officials, used Islamic qāḍī and state (maẓālim) courts, and related to each other using recognizably Islamicate conventions. This shift has emerged largely through study of documents preserved in the Cairo Geniza (produced mainly in Fatimid and Ayyubid Egypt and Syria, c. 1000-1250), and has in turn helped explain many aspects of these documents overlooked by older models. At the same time, it brings into question aspects of Jewish communal life that once seemed self-evident. If Jewish communities did not operate as hermetically sealed hierarchies, what held them together as relatively cohesive social groups? How did Jewish communal leaders cultivate and maintain loyalty? How did they exert authority given their lack of access to hard coercive powers? And why did Jews who could and did freely use Islamic legal venues nonetheless consistently choose to litigate arguments and document transactions in Jewish courts as well? This paper will approach these questions in the context of legal practice in rabbinic courts. I will argue that among other factors, Jewish judges and scribes drew authority and prestige from a set of notions about religious law shared broadly throughout the Islamic Middle East in the “Middle Periods,” although their implications for non-Muslims never became an explicit focus of Islamic legal or political thought. The first half of the paper will use anecdotal evidence from the Geniza to consider how these ideas shaped Fatimid and Ayyubid officials’ stance towards Jewish courts; in the second half, I will consider Geniza legal documents’ forms and formulae as evidence for their impact on Jewish officials’ own self-presentation.