Halakhah zu Schemot 28:41

That is that He commanded us to appoint judges and officers to force the implementation of the Torah's commandments and to bring those inclining away from the true path back towards it. And they will command to do the good and to come back from evil and will establish fences for the transgressor, such that the commandments and prohibitions of the Torah will not be decided according to the beliefs of each individual. And from the stipulations of this commandment is that these judges be one level above another. And that is when twenty-three judges are appointed in every city, all of them gathering in one place, in the gate of the city which is fit for this number. And these are the minor Sanhedrins. And the Great Court in Jerusalem is appointed of seventy judges. And one [judge] is appointed over these seventy, and he is the head of the yeshiva; and he is the one that the Sages also called the Nassi. And they are all gathered in one place designated for them. And a city with few inhabitants which is not fit for a minor Sanhedrin must appoint three [judges] to administer the minor laws; and the complicated matter they bring to the [court] above them. And they appoint officers [that] supervise the people. They go around the city, in the marketplaces and the streets, and observe the actions of the people in their carrying forth - until no injustice is done, even in a small matter. And the statement in which the commandment appears is His saying, "Judges and officers shall you appoint for yourself in all of your gates" (Deuteronomy 16:18). And the language of the Sifrei (Sifrei Devarim 144:1-4) is, "From where [do we know] that we appoint a court [...]? [Hence] we learn to say, 'Judges [and officers…].' [...] And from where [do we know] that we appoint one over all of them? [Hence] we learn to say, 'shall you appoint for yourself.' [...] And from where [do we know] that we appoint a court for each tribe? [Hence] we learn to say, 'for your tribes.' [...] 'and they shall judge the people' - [even] against their will." And this command of appointing seventy elders has already been repeated; and that is His, may He be exalted, saying, "Gather for Me seventy men" (Numbers 11:16). And they said (Sifrei Bamidbar 92:1), "Wherever 'for Me,' is stated, it surely endures [forever]; like [with the priests], 'that they minister for Me' (Shemot 28:41)." That means to say it is not a temporary commandment, but it is [intrinsically] fitting, and obligatory for all generations. And you should know that all of these appointments - meaning great Sanhedrins, minor Sanhedrins, courts of three and other appointments - are indeed done in the Land of Israel. And when there is ordination in the Land of Israel, it is then possible for those ordained to judge in the Land and outside of the Land. But they may not judge capital cases - whether in the Land or outside of the Land - unless the Chosen [Temple] is standing, as we explained at the beginning of the essay. And the language of the Sifrei (Sifrei Zuta, brought in Yalkut Shimoni on Torah 788:12) about His saying [about] one who smites a soul inadvertently, "Such shall be for you," saying, "in all your settlements" - "perhaps the cities of refuge should also be practiced outside the Land of Israel. [Hence] we learn to say, 'these.' These judges practice whether in the Land or outside the Land. But cities of refuge are only practiced in the Land." And the regulations of this commandment have already all been explained in Sanhedrin. (See Mishneh Torah, The Sanhedrin and the Penalties within their Jurisdiction 1)

To appoint judges and officers: To appoint (see Sefer HaMitzvot LaRambam, Mitzvot Ase 176) judges and officers that coerce [others] to do the commandments of the Torah, bring those that are veering from the path of the truth back to it against their will, order that which is fitting to do, prevent disgusting things and enforce the fences against the transgressor - so that the commandments and the preventions of the Torah not require the belief (acceptance) of each and every person. And it is from the conditions of this commandment that these judges should be one level above the other. That is that we set up twenty-three judges in each and every city that is fit for this number, all gathered together in one place from the gates of the city - and that is called a small sanhedrin. And in Jerusalem, we set up a large court of seventy judges, and we stand up one [judge] over these seventy and he is called the head of the academy - and he is the one that the Sages also called, nassi - and they would all be gathered in their place that is designated for them. And in a place that is small of number, such that it is not fit for a small sanhedrin, they should stand up three [that] should judge the small thing and they bring the difficult thing to the [court] that is above them. And likewise do they appoint supervisors among the people that circulate in the city, the markets and the streets [and] observe the matters of people in commercial buying and selling - so that there not be wrongdoing, even with a small thing. And the commandment that comes about this is that which He, may He blessed, stated (Deuteronomy 16:18), "Judges and officers shall you place for yourself in all of your gates." And the language of Sifrei Devarim 144 (and see Sanhedrin 16b), "From where [do we know] that we appoint a court for all of Israel? [Hence] we learn to say, 'Judges and officers.' And from where [do we know] that we appoint one [judge] on top of them all? [Hence] we learn to say, 'shall you place for yourself.' And from where [do we know] that we appoint a court for each and every tribe? [Hence] we learn to say, 'in all of your gates.' Rabban Shimon ben Gamliel said, '"For your tribes and they shall judge" - [that] is a commandment on each and every tribe to judge its tribe; "and they shall judge the people" - against their will.'" And this commandment to appoint seventy elders has already been repeated, and that is His, may He be blessed, stating to Moshe, peace be upon him, "Gather for Me seventy men" (Numbers 11:16). And they, may their memory be blessed, said (Sifrei Bamidbar 92), "Every place that it is stated, 'for Me,' behold it is an observance forever; and so [is it], 'And they shall be priests for Me, etc.' (Exodus 28:41)" - meaning to say, that it is a permanent commandment and not just temporary, but rather all of the days of the earth.