FORGED — this document is not what it claims to be, or its attribution is contested. See the summary.
A collection of some hundred papal letters attributed to popes of the first three centuries, almost all of them fabricated in ninth-century Francia, mixed in among genuine canons so that the whole reads as one archive. Their purpose was to protect bishops from their metropolitans and from lay lords by making every serious case appealable to Rome — and their long effect was to supply the high medieval papacy with an ancient pedigree it never had. ⚠ Jaffé's register is where each piece is marked.
not seriously doubted before the fifteenth century and not conclusively demolished until the seventeenth; every decretal of the ante-Nicene popes in later canon law comes from here
Received it
from 852 — Hincmar of Reims (Affirms). Isidore's forgeries were known among the Franks as early as 852, and Hincmar quotes a false decretal of Stephen I among the statutes of a council; though he suspected one or other document had been forged in part, he offered no objection to the collection as a whole. New Advent (Fathers and Catholic Encyclopedia) · Catholic Encyclopedia (1909), s.v. 'False Decretals'
22 January 865 — Pope Nicholas I (Affirms). In his letter of 22 January 865 on Rothad of Soissons' appeal, Nicholas reproached the Frankish bishops with quoting the letters of the early popes — Isidore's forgeries — when it served them and repudiating them when it did not, and put the theory of appeals much as Isidore had put it. New Advent (Fathers and Catholic Encyclopedia) · Catholic Encyclopedia (1909), s.v. 'False Decretals'
1140 — Gratian (Affirms). When Gratian wrote his Decree in 1140 he borrowed extensively from Isidore's collection — which is how the forgeries passed into the working law of the western church. New Advent (Fathers and Catholic Encyclopedia) · Catholic Encyclopedia (1909), s.v. 'False Decretals': 'when in 1140 Gratian wrote his Decree he borrowed extensively from Isidore's collection'
Refused it
1559 — The Centuriators of Magdeburg (Rejects). The Lutheran Centuries put the question squarely before the learned world for the first time. New Advent (Fathers and Catholic Encyclopedia) · Catholic Encyclopedia (1909), s.v. 'False Decretals': 'the Centuriators of Magdeburg, in 1559, put the question squarely before the learned world'
1628 — David Blondel (Rejects). Blondel's decisive study of 1628 settled it: since then the apocryphal nature of the decretals of Isidore has been an established historical fact. New Advent (Fathers and Catholic Encyclopedia) · Catholic Encyclopedia (1909), s.v. 'False Decretals', on Pseudo-Isidorus et Turrianus vapulantes (1628)