This paper will argue that the principle of a lacuna in Shi’i law can empower jurists to go beyond the traditional parameters of the shari’a. The principle allows for an expansion of Islamic law since jurists can legislate laws that have not been explicitly prohibited by textual sources. I will demonstrate that, in the past, Shi’i jurists often appealed to local customary practices in legislating laws that were absent in revelatory sources. This juridical practice is premised on the view that all reasonable beings accept and behave according to common norms and values. I will argue also that, based on the principle of the custom of reasonable people, jurists can deploy American social norms and customs as a source of new legislation. Such considerations can lead to a radically different formulation of diasporic jurisprudence.