Roman emperors Honorius and Theodosius II issue a new law requiring Novatianists to hold Easter celebrations at the same time as all other Christians. Novatianists are followers of Antipope Novatian who believe that the lapsi, or "lapsed Christians" who had renounced their faith during anti-Christian persecutions, should be refused communion and denied readmission to the Christian church.
According to the new Roman law:
We do not permit to go unavenged that transgression ... practiced by accursed men in violation of the sacred law, and especially by those deserters and fugitives from the company of the Novatians... if the Novatians should suppose that the day of Easter... ought to be celebrated on another day than that observed by the orthodox bishops, deportation as well as proscription shall be imposed.
Against them an even more severe punishment should have been announced, since in this crime they even surpass the insanity of the heretics by observing the festival of Easter at another time than that of the orthodox, and thus they venerate almost another Son of God than the one whom We worship." [CTh 16.6.6]
Novatianists called themselves "katharoi" or "Puritans" because of their desire to uphold a pure Christian faith and pure Christian community. Novatianism had been declared heretical in 251 for denying that the Christian church could grant absolution for certain sins, like renouncing one's faith. Novatian was one of the very first antipopes.