Council of Chalcedon, Canon VIII

Let the clergy of the poor-houses, monasteries, and martyries remain under the authority of the bishops in every city according to the tradition of the holy Fathers; and let no one arrogantly cast off the rule of his own bishop; and if any shall contravene this canon in any way whatever, and will not be subject to their own bishop, if they be clergy, let them be subjected to canonical censure, and if they be monks or laymen, let them be excommunicated.

Translation: Henry R. Percival, The Seven Ecumenical Councils, NPNF II.14 (1900), via CCEL.