Fatwas from Islamic organizations are prominent elements of public debates in democratic Indonesia, as well as the broader Muslim world. Yet scholars lack a clear theoretical explanation for the power of fatwas in politics. This paper draws on original archival material to explicate the legal authority of the fatwas from the Indonesian Council of Ulama (Majelis Ulama Indonesia, MUI), which over the past twenty years has become one of the country’s most influential actors. The paper distinguishes three periods in the growth and transformation of MUI; starting with charismatic authority and state corporatism, MUI later gained formal regulatory authority, and then authority through agenda setting, lobbying, mass mobilization, and the threat of violence. In light of the changing nature of MUI’s power and the concomitantly changing authority of its fatwas, the paper argues that contemporary fatwas contain no innate authority, nor do they have any inherent effects. Classical theories of Islamic law, Max Weber’s typology, and ethical theories of fatwas cannot explain MUI’s growing power or its modes of authority. To understand MUI’s growing power, it is necessary to look beyond these traditional modes of Islamic legal authority to modern organizational forms and their attendant strategies for exerting social control. In the modern age, Islamic legal authority reflects the dominant logic of political authority in society.