Objection 1. It would seem that a man can justly judge one who is not subject to his jurisdiction. For it is stated (Daniel 13) that Daniel sentenced the ancients who were convicted of bearing false witness. But these ancients were not subject to Daniel; indeed they were judges of the people. Therefore a man may lawfully judge one that is not subject to his jurisdiction.
Objection 2. Further, Christ was no man's subject, indeed He was "King of kings and Lord of lords" (Apocalypse 19:16). Yet He submitted to the judgment of a man. Therefore it seems that a man may lawfully judge one that is not subject to his jurisdiction.
Objection 3. Further, according to the law [Cap. Licet ratione, de Foro Comp.] a man is tried in this or that court according to his kind of offense. Now sometimes the defendant is not the subject of the man whose business it is to judge in that particular place, for instance when the defendant belongs to another diocese or is exempt. Therefore it seems that a man may judge one that is not his subject.
On the contrary, Gregory [Regist. xi, epist. 64 in commenting on Deuteronomy 23:25, "If thou go into thy friend's corn," etc. says: "Thou mayest not put the sickle of judgment to the corn that is entrusted to another."
I answer that, A judge's sentence is like a particular law regarding some particular fact. Wherefore just as a general law should have coercive power, as the Philosopher states (Ethic. x, 9), so too the sentence of a judge should have coercive power, whereby either party is compelled to comply with the judge's sentence; else the judgment would be of no effect. Now coercive power is not exercised in human affairs, save by those who hold public authority: and those who have this authority are accounted the superiors of those over whom they preside whether by ordinary or by delegated authority. Hence it is evident that no man can judge others than his subjects and this in virtue either of delegated or of ordinary authority.
Reply to Objection 1. In judging those ancients Daniel exercised an authority delegated to him by Divine instinct. This is indicated where it is said (Daniel 13:45) that "the Lord raised up the... spirit of a young boy."
Reply to Objection 2. In human affairs a man may submit of his own accord to the judgment of others although these be not his superiors, an example of which is when parties agree to a settlement by arbitrators. Wherefore it is necessary that the arbitrator should be upheld by a penalty, since the arbitrators through not exercising authority in the case, have not of themselves full power of coercion. Accordingly in this way did Christ of his own accord submit to human judgment: and thus too did Pope Leo [Leo IV] submit to the judgment of the emperor [Can. Nos si incompetenter, caus. ii, qu. 7.
Reply to Objection 3. The bishop of the defendant's diocese becomes the latter's superior as regards the fault committed, even though he be exempt: unless perchance the defendant offend in a matter exempt from the bishop's authority, for instance in administering the property of an exempt monastery. But if an exempt person commits a theft, or a murder or the like, he may be justly condemned by the ordinary.
Source: Summa Theologica (New Advent)