Jean Barbeyrac is best known as the leading eighteenth-century translator in French of the major writings on natural law by Pufendorf, Grotius and Cumberland. This article attempts to expound and assess Barbeyrac's independent contribution to the natural law tradition as it may be recovered both from these editions of the works of others and also from other writings. It is argued that Barbeyrac's intellectual context in the Huguenot diaspora and his distinctive reading of Locke, Bayle, and Pufendorf led him to develop an original equation of the authority of conscience with the authority of reason. The rationalist natural law theory he developed inevitably identified the role assigned to God within it and the scope of resistance to legal civil authority as central issues for debate which remained problematic for Barbeyrac throughout his career. These important ethical subjects remained unresolved in the general development of natural jurisprudence in the early eighteenth century, as exemplified in Barbeyrac's attempt to refute Leibniz's telling critique of Pufendorf.