Chartularium universitatis Parisiensis, I, 154.
A decretal was a pronouncement by the pope having the force of law, like an imperial constitution in the realm of civil law. The body of decretals may be compared to the Code of Justinian, just as the Decretum of Gratian, compiled in the twelfth century, may be likened to the Digest. Decretum and decretals were the chief texts lectured upon in canon law. Gregory IX herewith publishes an official collection of the decretals in five books drawn up by his chaplain, Raymond of Penãfort. At the end of the century Boniface VIII added a sixth book Liber sextus while Clement V of the early fourteenth century issued the Clementenes. These, too, became the subject of lecture courses and commentaries by the canon lawyers. Decretals outside of these collections were called extravagantes (that is, wandering without) and included the decretals of John XXII and extravagantes communes extending down to the time of Sixtus IV (1471- 1484).
The king of peace with pious miseration disposed his subordinates to be chaste, pacific and modest; but unbridled cupidity, prodigal of her gifts, envious of peace, mother of strife, matter of contention, daily generates so many new lawsuits that unless justice by its virtue repressed these attempts and explained the questions involved, the abuse of litigation would extinguish the rights of mankind, and concord, given a writ of divorce, would go forth beyond the boundaries of the world. And so the law is given to limit noxious appetite by rule of right, by which the human race is informed how to live aright, not harm another, and render to each his due. Divers constitutions and decretal letters of our predecessors are dispersed in varied volumes. Some of these canons were repetitious, others contradictory, others produced confusion by their prolixity. Yet others were scattered about outside the aforesaid volumes, and their uncertain authority made the decision of cases vary frequently. We therefore have provided, for the common utility and that of students especially, that these be collected in a single volume by our cherished son, brother Raymond, our chaplain and penitentiary, excluding the superfluous and adding our constitutions and decretal epistles, by which some matters which before were in doubt are settled. Wishing, therefore, that all use this compilation alone in cases and classrooms, we strictly prohibit that anyone presume to make any other without the special authority of the apostolic see. Given at Spoleto, September 5, in the eighth year of our pontificate.