Different interpretations exist regarding Khubilai’s 1280 edict prohibiting the Muslim method of slaughtering sheep and the practice of circumcision. By analyzing primary sources in the Chinese and Persian languages this article provides a new translation of the original text of the edict, showing that the Yuan established as a guiding principle that each subject group should follow its own customs. This article argues that the Yuan government prohibited the two Muslim practices because Mongol rulers believed that Muslims violated the guiding principle by forcing other peoples to follow the two practices. This article further argues that the Yuan court insisted on each group following its own customs because the power structure and legal system of the Mongol-Yuan Empire largely rested on differences and boundaries.