Pope Gregory IX was head of the Catholic Church and the ruler of the Papal States from 19 March 1227 until his death in 1241. He is known for issuing the Decretales and instituting the Papal Inquisition, in response to the failures of the episcopal inquisitions established during the time of Pope Lucius III, by means of the papal bull Ad abolendam, issued in 1184.
Gregory IX in a manuscript miniature c. 1270
Page from a late 13 c. copy of the Decretals of Gregory IX, now in the Biblioteca Medicea Laurenziana, Florence
Fanciful 16th c. fresco depicting Gregory excommunicating Frederick II in the Sala Regia, by Giorgio Vasari. Since few details where provided to the artist, the excommunication scene is given generically. Fredrick is shown pointing to a book with the word "Concilium" shown, possibly a reference to the general council that the emperor attempted to call to depose Gregory.
The Decretals of Gregory IX, also collectively called the Liber extra, are a source of medieval Catholic canon law. In 1230, Pope Gregory IX ordered his chaplain and confessor, 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.
Gregorius IX Decretales, c. 1290, Biblioteca Medicea Laurenziana, Florence
Gregory IX is portrayed among the great lawgivers of history by a bas-relief in the US House of Representatives chamber
Bernard of Botone, Casus longi super quinque libros Decrease, 1475
