Diana Kim challenges the conventional wisdom about opium prohibition—that it came about because doctors awoke to the dangers of drug addiction or that it was a response to moral crusaders—uncovering a more complex story deep within the colonial bureaucracy. Drawing on a wealth of archival evidence across Southeast Asia and Europe, she shows how prohibition was made possible by the pivotal contributions of seemingly weak bureaucratic officials. Comparing British and French experiences across today’s Burma, Cambodia, Laos, Malaysia, Singapore, and Vietnam, Kim examines how the everyday work of local administrators delegitimized the taxing of opium, which in turn made major anti-opium reforms possible.