Deuteronomy – 16:18 – You shall set up judges and law enforcement officials for yourself in all your cities that the Lord, your God, is giving you, for your tribes, and they shall judge the people [with] righteous judgment.

Gemora Sanhedrin 16:2 – this verse teaches that it is an obligation to set up judges and law enforcement officials in each city.

Torah Temimah Colloquial Translation of note #76
In a nearby Gemora on the same page an opinion is stated to set up judges and law enforcement officials for each tribe. Tosafot writes that if there is in a given city people from two tribes, then there is an obligation to set up two court systems; one for each tribe in that city.

It appears that Tosafot are answering the apparent contradiction of how one can set up a court system [simultaneously] in each city and also one for each tribe. For that reason, they explain that sometimes it is necessary to set up two court systems in one city if there are members of two tribes in that city.

However, in my opinion, that is a forced explanation. According to that line of thinking if one were to have a city with inhabitants from ten tribes, it would be necessary to set up ten court systems in [just] one city. Being that it was common to have more than one tribe in a given city, it would [often] be necessary to set up ten court systems in a single city. Logic does not incline towards such an explanation.

Therefore, it appears that the explanation is as follows: in addition to the requirement to set up a court system in each city, it is also required to set up one central court system per tribe (no matter what city they are in) to cover the entire land of Israel. This central court, for a given tribe, would have jurisdiction over tribal matters even though the members of that tribe may be scattered in many different cities. With this method, it comes out that each Jewish person in Israel would be under the jurisdiction of two court systems – one for his city and one for his tribe. Perhaps this is the intent of Rabbi Shimon Ben Gamliel’s statement that it is a commandment for each tribe to judge its own.

DBS Note: I found this note amazing because the Torah Temimah is basically rejecting an opinion that pre-dated him by approximately 800 years because it didn’t seem logical to him. Usually, I think he cites other commentators to support his critique but in this note he does not do that.