Well contrary to popular belief, there was no official "council" that decided what should or shouldn't be in the New Testament. But the 27 books were written before 70 AD, while the so-called "banned" books (actually gnostic texts) were produced no earlier than 150 AD and contain bizarre, heretical doctrine.
But I see your point.
‘But the 27 books were written before 70 AD’
that is up for debate...it’s entirely possible that none of the Gospels and Revelation predated 70 AD...