Hincmar, archbishop of Reims 845–882, placed strong emphasis on written law, as numerous surviving manuscripts and many treatises attest. This chapter analyzes that emphasis, exploring Hincmar’s classification of different kinds of legal norms, including church councils, papal decrees, biblical rules, and royal edicts. It then tracks how he applied the law in three case studies: the divorce of King Lothar II in 860; the rebellion of the archbishop’s own nephew Hincmar, bishop of Laon, in 870; and the Council of Saint-Macre in 881, of which Hincmar was the guiding spirit. Although Hincmar’s direct influence on legal tradition was relatively small, the chapter argues that his indirect influence was much greater, inasmuch as Hincmar raised the level of legal debate in late-Carolingian Francia.