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 XVIII

Canon XVIII.

If any bishop ordained to a parish shall not proceed to the parish to which he has been ordained, not through any fault of his own, but either because of the rejection of the people, or for any other reason not arising from himself, let him enjoy his rank and ministry; only he shall not disturb the affairs of the Church which he joins; and he shall abide by whatever the full synod of the province shall determine, after judging the case.

Notes.

Ancient Epitome of Canon XVIII.

Let a bishop ordained but not received by his city have his part of the honour, and offer the liturgy only, waiting for the synod of the province to give judgment.

Balsamon.

In canon xvij. the fathers punished him who when ordained could not be persuaded to go to the church to which he was assigned.  In the present canon they grant pardon to him who is willing to take the charge of the diocese, for which he was consecrated, but is prevented from doing so by the impudence of the people or else by the incursions of the infidel; and therefore they allow him to enjoy, in whatever province he may happen to be, the honour due his rank, viz., his throne, his title, and the exercise of the episcopal office, with the knowledge and consent of the bishop of the diocese.  He must not, however, meddle with the affairs of the church of which he is a guest, that is to say he must not teach, nor ordain, nor perform any episcopal act without the consent of the bishop of the diocese; but he must observe quiet, until he learns what he ought to do by the determination of the full Synod.

Aristenus explains that by keeping quiet is intended that he should not “use any military help or other power.”

This canon is found twice in the Corpus Juris Canonici, Gratian’s Decretum, Pars I., Dist. xcii., c. iv. and v.; in the versions of Martin Bracarensis and of Dionysius.