The important bit is that an individual rabbi cannot overturn anything; the power comes from a legislative entity called "The Sanhedrin". However, in order to b

The important bit is that an individual rabbi cannot overturn anything; the power comes from a legislative entity called "The Sanhedrin". However, in order to be part of the sanhedrin you need to be ordained by another member of the sanhedrin and at some point (unknown exactly when, possibly around the year 400) this lineage was lost. The idea of overturning a prophet doesn't really matter though, because as far as I know we don't get laws from the prophets (except Moses obviously).