Q. Mishneh Torah forbids putting converts in any position of authority, including overseeing conversions. This is found in the Laws of Kings and Wars 1:5. Whoever imagines that the term “seraroth” (positions of authority) used in this law couldn’t apply to officiating over conversion must not have read the law, which reads plainly, “…even over an irrigation channel”. Is commanding the transformation of the souls of righteous, God-fearing human beings less of a charge than an irrigation ditch?
A. Mishne Torah mentions nothing of Jews commanding the transformation of souls, unless one wants to force it in between the lines. Sounds like a teaching of the "Ari." We do not regard the "Ari" as a valid source of halakha. Conversion is a change in the legal status of a person of non-Israelite origin in relation to how the community of Israel is to relate to that individual within the framework of Torah. The person converting remains the same person. This is why a convert who murdered an Israelite before conversion is liable for the death penalty even after he converts (Hil. Melakhim 10,6 ). The description of a convert as being like a new-born is only a figure of speech. This figure of speech is used because the process of conversion as understood by the Talmudic Sages was supposed to be parallel to his coming to the faith of Israel -- not several years later. In fact, the Hebrew term "hozer" is used in reference to one who turns to the Jewish faith (ie: converts) just as it is used in reference to a native-born Israelite who repents, who is "hozer b-teshuva." In both cases, whether a convert or a born-Jew, when an individual abandons a lifestyle contrary to G-d's Will and aligns his behavior with Torah, he is described as being born anew (Ps. 51,11-12; Ez. 36,26).
The prohibition of a convert being appointed to the ministerial position of overseeing irrigation channels is when he is appointed to that office with legal authority. Does the one asking the question want to prohibit the convert from irrigating even the convert's own field? The entire context of Hil. Melakhim 1,5 is that of governmental positions of authority. Ripping this restriction out of context and applying it to just any position a convert may be in becomes absurd. Does a convert need to refuse a job promotion if he is offered a management position in a modern Israeli office full of born-Jews? Is this less than being in charge of an irrigation ditch? Should a convert be forbidden from leading Jewish prayers, whether in "Ohel Moshe" or other minyanim? Is leading 10 or more Jews in prayer a lower position than being in charge of an irrigation ditch? Perhaps a convert should be forbidden from marrying a born-Jewish female. In doing so, he is put in a position of authority over a born-Jew. The argument is ridiculous.
“A king should not be appointed from among converts, not even from a convert's descendants after many generations, unless the descendant’s mother is a native-born Israelite, for Deuteronomy 17,15 states: 'You may not appoint a foreigner who is not one of your brethren.' This restriction does not apply to the monarchy alone, but to all positions of authority within Israel: not as an army commander, not as a leader of fifty, nor as a leader of ten. He may not even supervise the allocation of water from a stream to various fields. Needless to say, a judge or a nasi should only be a native-born Israelite [i], as it is stated (ibid.): 'Appoint a king over you from among your brethren.' This implies that all appointments must only be 'from your brethren.'"
Hilkhoth Melakhim 1,5 prohibits the people of Israel from establishing over themselves (ie: over native born Israelites) someone of non-Israelite origin to a position of governmental / ministerial office. This law prohibits a convert from being in such a ministerial office whether it is over 50 Israelites or even over 10. This halakha does not go lower than the number ten, other than when acting as a judge. Earlier in Mishneh Torah, in Hilkhoth Sanhedrin 2,12 , it is made clear that the prohibition against a convert being included in a Jewish court of three applies when that court of three adjudicates a native born Israelite. See the video below for furthur clarification. However, Hil. Sanhedrin 11,12  states that a convert can sit in judgment of another convert, and even a non-Israelite can sit in judgment over non-Israelites (Hil. Melakhim 10,14 ).
In conclusion, Hil. Melakhim 1,5 only prohibits a convert from being established to a ministerial office over native born Israelites. When a potential convert goes into the miqwa (pool of water for ritual immersion), the potential convert is not a native born Israelite! And when he comes out of the water, he is still not a native born Israelite. In other words, Hil. Melakhim 1,5 cannot reasonably be used to invalidate conversions that were overseen by individuals who themselves converted.
We’re in favor that only kosher born-Jews oversee conversions, not because conversions would be invalid otherwise, but rather so as to remove as much doubt in people's minds as possible. The only reason our beth din does not currently consist entirely of born Jews is due to the fact that three born Jews have not risen up to the challenge. If you know any born Jews who affirm our fundamentals, share our vision, and are who are willing to step up to the plate and work with us, please let us know!
R' Yosef Eliyah
[i] There are several known examples of converts who held valid positions of authority in ancient Israel, both as judges and even as nasi. Shmaya and Avtalyon are well known examples,(גיטין נז ע"ב) as is Ribi Aqiva. Thus, the broad restriction on converts serving as judges over Israelites seems to be a later Rabbinic injunction; otherwise, we may need to call into question the validity of all halakhoth that were influenced by Shmaya, Avtalyon, Ribi Aqiva, and others. There's one problem -- these three converts influenced the entirety of Talmudic law.