After the Emperor Constantine began the process of tolerating then adopting Christianity, councils flourished. The Council of Nicaea is the first Ecumenical (universal) council. The first four ecumenical councils, were given a special place in the traditions of the church.
Constantine and the Council of Nicaea (325) Caesaropapism
Tanner Texts and Translations
Decrees of the Ecumenical Councils, 1: Nicaea I-Lateran V, 2: Trent-Vatican II, ed. Norman P. Tanner. 2 Volumes. London-Washington, D.C.: Sheed & Ward and Georgetown University Press, 1990 (Greek-Latin texts with facing English translation)
Western Councils
Council of Arles 314 Called by Constantine --- Letter and canons sent to Pope Silvester
Council of Cologne 346 Trial of
Eufrata, who had denied Christ was God (Eufrata
Christum Deum negat)
Council of Valence 374 Ecclesiastical
discipline
Pope Gregory the Great
(590-604) compared the first four councils to the four Gospels. From the
mid-fifth century, the papacy claimed the right to approve the acts of
councils. The first eight Ecumenical Councils were held in the Greek
speaking Mediterranean.