In the early decades of the twentieth century, a heated debate over the legitimacy of Jewish mystical texts, foremost among them the Zohar, divided the Jews of Sanā, the Yemeni capital, into two camps. In 1914, one Jewish faction took the other to a Muslim court. There, a Muslim jurist heard arguments for and against Jews' study of the Zohar. The resulting fatwā sheds light on this fascinating moment of inter-religious dialogue. At issue here is the extent to which the Jewish litigants framed their arguments in Islamic terms and the ways in which the Muslim jurist and his employer, Imām Yahyā Hamīd al-Dīn, the theocratic ruler of Yemen, understood Judaism in terms borrowed from contemporary debates on Islamic sectarianism. The centrality of this fatwā in later permutations of the schism within Yemeni Judaism will be addressed as well.