In this new study, the author examines sijills, the official documents of the Ottoman Islamic courts, to understand how sharia law, society, and the early-modern economy of sixteenth- and seventeenth-century Ottoman Cairo related to the practice of custom in determining rulings. In the sixteenth century, a new legal and cultural orthodoxy fostered the development of an early-modern Islam that broke new ground, giving rise to a new concept of the citizen and his role. Contrary to the prevailing scholarly view, this work adopts the position that local custom began to diminish and decline as a source of authority. These issues resonate today, several centuries later, in the continuing discussions of individual rights in relation to Islamic law.