Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV: The Canons of the Councils of Ancyra, Gangra, Neocæsarea, Antioch and Laodicea, which Canons were Accepted and Received by the Ecumenical Synods.: Canon VI
If any one has been excommunicated by his own bishop, let him not be received by others until he has either been restored by his own bishop, or until, when a synod is held, he shall have appeared and made his defence, and, having convinced the synod, shall have received a different sentence. And let this decree apply to the laity, and to presbyters and deacons, and all who are enrolled in the clergy-list.
The sentence of the greater synod upon a clerk excommunicated by his bishop, whether of acquittal or condemnation, shall stand.
Compare Apostolic Canons numbers XII. and XXXII.
This canon is found in the Corpus Juris Canonici, Gratian’s Decretum, Pars II., Causa XI., Quæst. III, Can. ij.