What does the Halacha/Poskim say about a frum person becoming a judge in a secular court, where he may be required to rule in a non-halachic manner in cases involving Jews and non-Jews?
Answer:
This is a delicate question.
For criminal law, there is no problem, because Torah law recognizes the need for criminal law to curb crime and ensure the safety of law-abiding citizens (see Derashos Ha-Ran, Derush 11, who explains the need for a secular court of law in criminal law; Teshuvos Ha-Rashba echoes the same idea). Therefore, even when the defendant is Jewish, it is permitted to rule based on the principles of secular law. This is in addition to the binding nature of dina demalchusa.
The question arises principally for civil law. If the case involves two non-Jews, there is of course no problem. The same applies for a Jew and a non-Jew, where it can be assumed that the non-Jew will not be prepared to go to a Jewish court of law, and the Jew certainly agrees to the ruling of a secular court. Even for two Jews, who are not permitted to come to a secular court (even by mutual agreement; see Choshen Mishpat 26:1), there is no prohibition in passing judgment (see, for instance, Rashbash 331).
The main problem arises when one Jew summons another Jew to a secular court (in a civil law case), where the latter comes against his will. In this case, ruling that the defendant must pay according to secular law can constitute a problem, because according to Torah law he might be exempt (or might be obligated to pay a different amount). However, in many cases, such as cases involving corporations, or other matters directly addressed by secular law, it is possible to assume agreement. This is certainly true of non-religious Jews, and often true even of religious Jews, because the custom (whether permitted or prohibited) is to take such cases to secular courts.
Therefore, in general it is permitted to serve as a judge in secular courts. When confronted with a civil case, where the defendant is a religious Jew, it is best to offer a compromise between the sides.
The general “custom” is for Orthodox Jews to serve as judges in secular courts, and I have not seen rabbinic teshuvos prohibiting the practice. See also Eliav Shochetman, Mishpat Yisrael Le-Or Ha-Halachah, Techumin 13, p. 337.
