Law was one of the most important realms that set frameworks for transregional interactions among individuals, communities and institutions in the premodern world. It synchronised structures of exchange through commonly agreed practices and expectations. The written legal treatises, along with unwritten customs, norms and rituals, prescribed ideal forms of social, cultural, economic and political relations to maintain order, peace and affinity in the societies in which they operated. These written and unwritten laws influenced each other in the long run, both internally and externally, through spatial and temporal concurrences. While the unwritten laws of the premodern world may be inaccessible, the written texts provide a rich archive to understand the ways in which the communities struggled towards constructing an ideal world through the active and passive conversations of individual communities and institutions. In Monsoon Asia, the legal worlds of Buddhism, Hinduism and Islam, along with several minor traditions indigenous to specific lands and times, formed a cosmopolis of laws which expanded chronologically vertically and geographically horizontally. In the premodern period no tradition replaced another entirely. Instead, they all coexisted in a larger domain with fluctuating influences over time and place.