I. The relevant canons which addressed the status of Constantinople and are discussed by Balsamon

The following canons dealt directly with the canonical status of Constantinople:

Constantinople I (381), c.3

THE Bishop of Constantinople, however, shall have the prerogative of honour after the Bishop of Rome; because Constantinople is New Rome.

Chalcedon (451), c.28

FOLLOWING in all things the decisions of the holy Fathers, and acknowledging the canon, which has been just read, of the One Hundred and Fifty Bishops beloved-of-God (who assembled in the imperial city of Constantinople, which is New Rome, in the time of the Emperor Theodosius of happy memory), we also do enact and decree the same things concerning the privileges of the most holy Church of Constantinople, which is New Rome. For the Fathers rightly granted privileges to the throne of old Rome, because it was the royal city. And the One Hundred and Fifty most religious Bishops, actuated by the same consideration, gave equal privileges (isa presbeia) to the most holy throne of New Rome, justly judging that the city which is honoured with the Sovereignty and the Senate, and enjoys equal privileges with the old imperial Rome, should in ecclesiastical matters also be magnified as she is, and rank next after her; so that, in the Pontic, the Asian, and the Thracian dioceses, the metropolitans only and such bishops also of the Dioceses aforesaid as are among the barbarians, should be ordained by the aforesaid most holy throne of the most holy Church of Constantinople; every metropolitan of the aforesaid dioceses, together with the bishops of his province, ordaining his own provincial bishops, as has been declared by the divine canons; but that, as has been above said, the metropolitans of the aforesaid Dioceses should be ordained by the archbishop of Constantinople, after the proper elections have been held according to custom and have been reported to him.

Council in Trullo (Quinisext) (692), c. 36.

RENEWING the enactments by the 150 Fathers assembled at the God-protected and imperial city, and those of the 630 who met at Chalcedon; we decree that the see of Constantinople shall have equal privileges with the see of Old Rome, and shall be highly regarded in ecclesiastical matters as that is, and shall be second after it. After Constantinople shall be ranked the See of Alexandria, then that of Antioch, and afterwards the See of Jerusalem.

The texts here come from the most convenient collection of the canons in English - Henry R. Percival, ed., The Seven Ecumenical Councils, The Nicene and Post Nicene Fathers, 2nd series, ed. Philip Schaff & Henry Wace, Vol. XIV, (Grand Rapids, MI.: Eerdman, 1956: orig. ed, Oxford & New York: 1900). Future references are given as “Percival”.