The idea that a Jewish council was held in 90 A.D. that set the Jewish canon of scripture did not surface till the 19th century and was promoted by two German scholars – one being Heinrich Graetz. There is virtually no scholarly evidence, beyond a few scant rabbinical texts, that supports the historicity of this council. It is still discussed among some scholarly circles but mostly predicated with “myth” or “legend.”
Marc Zvi Brettler writes that the meager evidence from rabbinic texts informing us of this supposed council where the canon of scripture for the Jews was actually set is based largely on a misunderstanding of those rabbinic texts. Instead, the council was attempting to justify certain texts already considered canonical. One such book that was debated was the Song of Songs . Moreover Brettler also indicates that the Jewish cannon was not stabilized until sometime in the second century CE and the process of canonization was a gradual process and not a definitive act at the Council of Jamnia.
If this council did occur, then a big question arises as to “Why weren’t all the Jews invited?” The records show a heavy leaning towards the pharisaic understanding of the books. It appears that several groups were ignored, even the African Jews who considered the entire Septuagint as canonical.
Supposing the council of Jamnia set the canon for the Jewish scriptures in 90 A.D. and thereby Christians, as well as Jews, must follow the same canon raises serious theological questions about the nature of authority. First what gave this council of Rabbis, sans-Temple and possibly sans-priesthood, the authority to make a binding set of books for the entire Jewish faith? This is even more so when one wonders if the Sanhedrin and Scribes were present.
A second theological problem arises based upon the date of the council. Jamnia is said to have happened in about the year 90 A.D. What kind of authority can or does a Jewish Council, post-resurrection, have on the body of Christianity? To appeal to this council in an attempt to discredit the Catholic Old Testament canon is to essentially shoot ones self in the proverbial foot, for by discrediting the Canon with appeal to Jamnia is to give a group of Jewish rabbis authority over all of Christianity. This is a belief that is far from Christian. For Christ, from the Christian perspective, came to fulfill Judaism thereby rendering parts of Judaism nonbinding, or binding in a new way, to Christians.
If the Council of Jamnia occurred, as once thought, what it does tell us is that the Jewish Canon was not a unified, settled, definitive work before the year 90 A.D. Examples of this can easily be found through history. The Ethiopian Jews had a different Canon by accepting all of the Septuagint. The Sadducees only accepted the books of Moses and authoritative scriptures, while the Pharisees accepted more. More recently, the Dead Sea Scrolls have been shedding light on the history of the Jewish canon to a further degree with a now incomplete book of Psalms, which appears to have been used in a fashion similar to modern prayer books. The Dead Sea Scrolls also have a canon more akin to the Septuagint except written in Hebrew instead of Greek.
Therefore, for a non-Catholic to appeal to the Council of Jamnia as proof that the Catholic canon is not the Old Testament for Christians is to hang one’s coat on a broken hook. It ignores history, promotes bad theology, and disregards Jewish culture and the multiplicity of Jewish canons in existence at the time of at the time of the Apostles and the very early church.
 Berlin, Adele, Marc Zvi. Brettler, and Michael A. Fishbane. "The Canonization of the Bible." The Jewish Study Bible: Jewish Publication Society Tanakh Translation. Oxford: Oxford UP, 2004. 2072-077. Print.