Liber Extra
The Decretals of Gregory IX (Latin, Decretales Gregorii IX), also collectively called the Liber extra, are a source of medieval Canon Law. In 1230, Pope Gregory IX ordered his chaplain and confessor, St. Raymond of Penyafort, a Dominican, to form a new canonical collection destined to replace the Decretum Gratiani, which was the chief collection of legal writings for the church for over 90 years. It has been said that the pope used these letters to emphasize his power over the Universal Church.