This chapter explores the general characteristics of, and the role of law among, early Muslim communities of the Indian Ocean world in the seventh to the tenth centuries, a period usually understood as the formative and classical period of Islamic law. After dividing the oceanic littoral into five major zones on the basis of early Islamic settlements and identifying five functional groups of Muslim itinerants, I explore how the Muslims functioned within the existing physical and social structures, with or without following a particular legal paradigm. Did Muslims manage their own laws or did they operate under other legal regimes, and how did Islamic law appear in those places to administer a partly mobile and partly sedentary community?