Based on the following Scriptures, our conclusion is that the disciples or followers of Yahshua - not the orthodox Jews -are the ONLY ones who can legitimately hold the position of the lawgiver TODAY, in the Bridegroom's bodily absence.
Colossians 2:8. See to it that no one makes a prey of you through philosophy and vain deceit, according to the traditions of men....and not according to MessiYah....  You have been made complete in Him (YAHSHUA) who is the Head of all principality and AUTHORITY....  Let no one therefore judge you...in respect of the Feasts, New Moons, or Shabbat,  ...except the body/assembly of MessiYah.  Let no one deprive you of the prize; one who takes delight in false humility...taking his stand on what he has not seen, puffed up (e.g. with the leaven of the Pharisees) by his own fleshly mind....  If then you died with MessiYah....why do you subject yourselves to regulations...  according to the commandments and teachings of men,  which only have an appearance of wisdom in self-imposed worship...?
In contradistinction to the traditions of men and leaven of the Pharisees, Shaul (Paul) clearly says "Let no one judge...concerning the Feasts...except the assembly of MessiYah". If you do not have YAHSHUA, it doesn't matter whether you're an Orthodox Jew, or Karaite, or member of the recently re-invented Jewish sanhedrin, etc. IF YOU DO NOT HAVE YAHSHUA, YOU HAVE NO AUTHORITY TO DETERMINE THE DATES OF THE FEASTS, because all authority in heaven and in earth was given to YAHSHUA, and upon His ascension, He transferred the authority on earth to His disciples.
Mattithyahu/Matthew 28:18. And YAHSHUA came up and spoke to them saying, "ALL AUTHORITY HAS BEEN GIVEN TO ME IN HEAVEN AND ON EARTH. (cf, Lk. 10:22; Jn. 3:35; 17:2)  Therefore go and make taught ones of all the nations....  teaching them to guard all that I HAVE COMMANDED YOU."
Ma'aseh/Acts 1:8 And YOU SHALL RECEIVE AUTHORITY, after that the Ruach HaKodesh is come upon you: and you shall be witnesses unto Me both in Yahrushalem, and in ALL YAHUDAH, and in Samaria, and unto the uttermost part of the earth.
Notice that YAHSHUA says the disciples who are endowed with HIS AUTHORITY will even be teaching ALL YAHUDAH; and NOT the other way around!
So who will you believe: YAHSHUA, who observed a 14th Passover along with the Sadducees/Karaites, and rose three days later on Bikurrim/Firstfruits, or the empty words of the rabbis who changed the calendar as part of a plan to discredit His Messiahship, and claimed that the disciples stole His body?
Mattithyahu/Matthew 6:24. "No man can serve two masters, for either he will hate the one and love the other, or he will cleave to the one and despise the other. You are not able to serve [YAHSHUA] and [the unbelieving rabbis]."
Yahchanan/John 12:26. "If any one serves Me, let him follow Me. And where I am, there My servant shall be also. If any one serves Me, My Father shall value Him."
Yahoshua/Joshua 24:15. "Choose you this day whom you are going to serve...but as for me and my house, we will serve YAHWEH / YAHSHUA."
It IS a matter of authority.