21 Lastly should be borne in mind the great weight and crucial test of history, by which it is plainly proved that the legislative and judicial authority of which We are speaking has been freely and constantly used by the Church, even in times when some foolishly suppose the head of the State either to have consented to it or connived at it. It would, for instance, be incredible and altogether absurd to assume that Christ our Lord condemned the long-standing practice of polygamy and divorce by authority delegated to Him by the procurator of the province, or the principal ruler of the Jews. And it would be equally extravagant to think that, when the Apostle Paul taught that divorces and incestuous marriages were not lawful, it was because Tiberius, Caligula, and Nero agreed with him or secretly commanded him so to teach. No man in his senses could ever be persuaded that the Church made so many laws about the holiness and indissolubility of marriage,(34) and the marriages of slaves with the free-born,(35) by power received from Roman emperors, most hostile to the Christian name, whose strongest desire was to destroy by violence and murder the rising Church of Christ. Still less could anyone believe this to be the case, when the law of the Church was sometimes so divergent from the civil law that Ignatius the Martyr,(36) Justin,(37) Athenagoras,(38) and Tertullian(39) publicly denounced as unjust and adulterous certain marriages which had been sanctioned by imperial law.
Source: Arcanum Divinae (Vatican.va)