Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Fourth Ecumenical Council.  The Council of Chalcedon.: Canon XVI

p. 280 Canon XVI.

It is not lawful for a virgin who has dedicated herself to the Lord God, nor for monks, to marry; and if they are found to have done this, let them be excommunicated.  But we decree that in every place the bishop shall have the power of indulgence towards them.

Notes.

Ancient Epitome of Canon XVI.

Monks or nuns shall not contract marriage, and if they do so let them be excommunicated.

Van Espen.

Since this canon says nothing at all of separation in connexion with a marriage made contrary to a vow, but only orders separation from communion, it seems very likely that vows of this kind at the time of the synod were not considered diriment but only impedient impediments from which the bishop of the diocese could dispense at least as far as the canonical punishment was concerned.

Hefele.

The last part of the canon gives the bishop authority in certain circumstances not to inflict the excommunication which is threatened in the first part, or again to remove it.  Thus all the old Latin translators understood our text; but Dionysius Exiguus and the Prisca added confitentibus, meaning, “if such a virgin or monk confess and repent their fault, then the bishop may be kind to them.”  That the marriage of a monk is invalid, as was ruled by later ecclesiastical law, our canon does not say; on the contrary, it assumes its validity, as also the marriages contracted by priests until the beginning of the twelfth century were regarded as valid.

This canon is found in the Corpus Juris Canonici, Gratian’s Decretum, Pars II., Causa xxvii., Quæst. I., canon xxii., from Isidore’s version; it is also found in Dionysius’s version as canon xij. of the same Quæstio, Causa, and Part, where it is said to be taken “ex Concilio Triburiensi.”