The collection contains important resources for the study of canon law from the sixteenth through the nineteenth century housed in the CRAI Law Library and Rare Book and Manuscript Library. These resources include the Decretum Gratiani and the Decretales Gregorii IX, as well as various commentaries and treatises.
Pope Gregory IX asked Raymond of Penyafort, his chaplain and confessor, to compile a new collection of canon law to replace the previous ones. The compilation was called simply the Decretals of Gregory IX (Decretales D. Gregorii papae IX svae integritati vna cvm glossis restitvtae…), and it was also known in Latin as the Liber extra. Fueron promulgadas en 1234 y estuvieron en uso en la Iglesia Católica hasta el Código de derecho canónico de Pío X (1917). The Decretals were instituted in 1234 and remained in use by the Catholic Church until 1917, when Pope Pius X instituted the Code of Canon Law. The Decretals represent an important effort to unify all Church law and put it under the control of the pope so that every ecclesiastical court applied the same law.