Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Canons of the Synods of Sardica, Carthage, Constantinople, and Carthage Under St. Cyprian, Which Canons Were Received by the Council in Trullo and Ratified by II. Nice.: Canon XV

Canon XV.

Of the divers orders who serve the Church, that if any one fall into a criminal business and refused to be tried by the ecclesiastical court, he ought to be in danger therefor; and that the sons of bishops (sacerdotum) are not to attend worldly shows.

Moreover it seemed good that if any bishop, presbyter, or deacon, who had a criminal charge brought against him or who had a civil cause, refused to be tried by the ecclesiastical tribunal, but wished to be judged by the secular courts, even if he won his suit, nevertheless he should lose his office.

This is the law in a criminal suit; but in a civil suit he shall lose that for the recovery of which he instituted the proceedings, if he wishes to retain his office.

This also seemed good, that if from some ecclesiastical judges an appeal was taken to other ecclesiastical judges who had a superior jurisdiction, this should in no way injure the reputation of those from whom the appeal was taken, unless it could be shown that they had given sentence moved by hatred or some other mental bias, or that they had been in some way corrupted.  But if by the consent of both parties judges had been chosen, even if they were fewer in number than is specified, no appeal can be taken.

And [it seemed good] that the sons of bishops should not take part in nor witness secular spectacles.  For this has always been forbidden to all Christians, so let them abstain from them, that they may not go where cursing and blasphemy are to be found.

Notes.

Ancient Epitome of Canon XV.

A bishop or cleric who has a criminal suit brought against him, if he leaves the Church and betakes himself to secular judges even if he had been unjustly used, shall lose his rank.  And if he was successful in his political affairs, if he follows this, he shall lose his own grade.  No appeal can be taken from the ecclesiastical judges, except they be proved to have given their decision beforehand moved thereto by a bribe or by hatred.  No appeal can be taken from the decision of judges chosen by each side.

This canon is made up of Canons ix., x., and xj. of the Council of Hippo, a.d. 393.

Johnson.

In this canon the African bishops made bold with the Civil Courts.  To lay such restraints on bishops and clergymen is, I am sure, very proper, to say no more.