תּלמוד אויף דברים 16:18

HALAKHAH: “Criminal courts apply in the Land,” etc. ⁷¹Tosephta Sanhedrin 3:10, Babli 7a.“Criminal courts apply in the Land and outside the Land, as it is written⁷²Num. 35:29.: This shall be for you a law statute for your generations, in all your dwellings. And why does the verse say⁷³Deut. 16:18., judges and marshals you shall appoint for yourself in all your gates, in the towns of the Land of Israel. Only that in the Land of Israel one installs judges in every town and outside the Land one appoints them by circuits.” It was stated: ⁷⁴Sifry Deut. 144, Babli Sanhedrin 16b. There and in the sources given in Note 71 the author is Rabban Simeon ben Gamliel.
The difference between the anonymous Tanna of the first Tosephta and R. Dositheos b. Yannai / Rabban Simeon ben Gamliel is that according to the first Tanna the claimant in a civil suit has the choice of the jurisdiction to file his suit whereas the dissenters restrict him to courts of his own tribe (L. Finkelstein, Commentary to Sifry).“Rebbi Dositheos ben Rebbi Yannai says, there is an obligation for every tribe to judge his own tribe, as it is written⁷³Deut. 16:18.: Judges and marshals you shall appoint for yourself in all your gates which the Eternal, your God, gives you for your tribes.”

If so then why does the Torah say (Deuteronomy 17,8) "In your gates"? In your gates [Isreal] you should set up courts in each and every district and in each and every city, but in the Diaspora you should set up [courts] in each and every district but you should not set up [courts] in each and every city.

Let's see [how it is redundant]. What does "atzeret" - "restraint" mean? Restraint from doing [halachically forbidden] work. But isn't it [already] written, (Deuteronomy 16:8) "You shall not do work"? Why does Scripture say that it [is a day of] "atzeret"? Learn out from this that it is free [for a gezeira shava through its redundancy].