In the history of canon law, the decretalists of the thirteenth century formed a school of interpretation that emphasised the decretals, those letters issued by the Popes ruling on matters of church discipline (epistolae decretales), in preference to the Decretum Gratiani (1141), which their rivals, the decretists favoured.Rhidian Jones, The Canon Law of the Roman Catholic Church and the Church of England: A Handbook (T&T Clark, 2000), 45–46.