Emperor Valentinian III decrees that if priests are involved in a legal dispute, they can have a bishop act as judge.
According to this decree:
"When a case arises between priests and if the litigants agree to it, a bishop will have the right to act as judge. This privilege We also grant for cases of laymen, if they agree.
Otherwise We do not allow the bishops to be judges because bishops do not have a law court and cannot have cognizance of cases except in religious matters..." [NV 35]
Valentinian III also issues an injunction against priests pursing any other line of work at the same time:
"We order that clerics must henceforth engage in no trade. If they want to engage in business, they will be subject to the judges and will not be protected by the privilege of clerics."
It's interesting that Valentinian III is aware of the fact that bishops don't understand that law, but will nevertheless allow them to act as a judge in disputes between priests. This only makes sense if Valentinian III assumes that the bishops won't render judgments based on traditional Roman law but instead based on church laws and Christian doctrine.