Question: "What happened at the Council of Jamnia?"
Answer: The 1st-century Council of Jamnia (Jabneh) is where the limits of the Jewish canon are said to have been finalized. This canon rejects the Apocrypha. Opinions about this council are varied and contradictory. The Roman Catholic Church, which accepts the Apocrypha as inspired Scripture, denies that such a council ever happened. Many non-Catholic scholars, who reject the Apocrypha, use the Council of Jamnia to bolster their claim that the Jewish canon had been settled and closed by the end of the first century and that the early church accepted this canon as binding.
Roman Catholic scholars counter that that there is no reason that Christians should accept the conclusions of the Council of Jamnia (if it ever happened at all), especially considering that the Jewish canon may have been influenced by the Jewish rejection of Christ and animosity against the early church. The Septuagint (the Greek translation of the Old Testament) was used extensively by the early Gentile Christians. Paul often quotes from it in his letters. The Septuagint contained the Apocrypha. Catholic scholars claim the rabbis may have rejected the Apocrypha precisely because it was in “the Bible of the early church.” (On a side note, even this argument demonstrates that the Apocrypha was treated differently than the rest of the Old Testament. For instance, the early church relied heavily upon Isaiah, but there was no Jewish rejection of Isaiah.)
As a rejoinder, many Protestants point out that the Roman Catholic Church never officially affirmed the Apocrypha as inspired until the Council of Trent (1545—1563). This affirmation was influenced by their rejection of Protestantism, which also rejected the Apocrypha.
If there were early documents that clearly recorded the activities of the Council of Jamnia, there might be fewer grounds for controversy. However, the existence of the council was first proposed in the mid-18th century based on inferences from earlier sources. There is no clear evidence that Jewish leadership held a specific council where the OT canon was settled once and for all. If such a council did happen, there is no way to determine if it was clearly “authoritative” because “official” Judaism was in disarray as the temple had been destroyed and the Jews were scattered across the Roman Empire.
While questions about the Council of Jamnia may be interesting from the standpoint of historiography, it seems that questions about whether or not the Apocrypha should be included in the canon of the Christian Bible are best settled on other grounds.