Charles Dumoulin (1500–1566) is one of the most famous jurists of early modern Europe. His Commentary on the Custom of Parisearned him a reputation as a brilliant jurist and as a founder of a unified French legal culture. Until the early twentieth century, French jurists considered engagement with Dumoulin’s work obligatory for a better understanding of the sources of Napoleon’s Civil Code. Yet Dumoulin was also a man of his age, torn by the growing divisions within Christianity and fascinated by the rise of nationalist interests. His hostility towards the pope and his condemnation of abusive practices within the Roman Catholic Church led to his becoming persona non gratain Paris, and he was forced into exile in Switzerland and Germany, where he met Calvinist and Lutheran theologians without ever losing his uncompromising temper and sense for individual autonomy. Dumoulin struggled to find a personal faith adapted both to his spiritual needs and to his concerns with the privileges of the Gallican Church and the French monarchy. The chapter highlights the impact of his Protestant sympathies on his ecclesiological and economic thought, particularly his call for a return to the primitive church and acceptance of moderate interest rates as a matter of principle.