Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Canons of the Councils of Ancyra, Gangra, Neocæsarea, Antioch and Laodicea, which Canons were Accepted and Received by the Ecumenical Synods.: Canon X

Canon X.

They who have been made deacons, declaring when they were ordained that they must marry, because they were not able to abide so, and who afterwards have married, shall continue in their ministry, because it was conceded to them by the bishop.  But if any were silent on this matter, undertaking at their ordination to abide as they were, and afterwards proceeded to marriage, these shall cease from the diaconate.

Notes.

Ancient Epitome of Canon X.

Whoso is to be ordained deacon, if he has before announced to the bishop that he cannot persevere unmarried, let him marry and let him be a deacon; but if he shall have kept silence, should he take a wife afterwards let him be cast out.

Van Espen.

The case proposed to the synod and decided in this canon was as follows:  When the bishop was willing to ordain two to the diaconate, one of them declared that he did not intend to bind himself to preserving perpetual continence, but intended to get married, because he had not the power to remain continent.  The other said nothing.  The bishop laid his hands on each and conferred the diaconate.

After the ordination it fell out that both got married, the question propounded is, What must be done in each case?  The synod ruled that he who had made protestation at his ordination should remain in his ministry, “because of the license of the bishop,” that is that he might contract matrimony after the reception of the diaconate.  With regard to him who kept silence the synod declares that he should cease from his ministry.

The resolution of the synod to the first question shews that there was a general law which bound the deacons to continence; but this synod judged it meet that the bishops for just cause might dispense with this law, and this license or dispensation was deemed to have been given by the bishop if he ordained him after his protestation at the time of his ordination that he intended to be married, because he could not remain as he was; giving by the act of ordination his tacit approbation.  Moreover from this decision it is also evident that not only was the ordained deacon allowed to enter but also to use matrimony after his ordination.…Moreover the deacon who after this protestation entered and used matrimony, not only remained a deacon, but continued in the exercise of his ministry.

On the whole subject of Clerical Celibacy in the Early Church see the Excursus devoted to that matter.

This canon is found in the Corpus Juris Canonici.  Decretum Pars I., Dist. xxviii, c. viii.