This chapter argues that in the early medieval period, Catholic law both reflected and reinforced a largely “horizontal” Church structure, in which bishops played a central role, often in close engagement with secular lords and rulers. The first part of the chapter surveys the types of existing evidence for early medieval Church law, from the Carolingians up until the Gregorian Reform of circa 1050. The second part focuses on continuities between the Carolingian reforms and the tenth and early eleventh centuries. Recent scholarship has increasingly argued that the Carolingian reforms did not end with the fragmentation of the Carolingian empire. Building on that work, this chapter describes three examples of continuities between the Carolingian and Ottonian periods.