It seems that many mitzvot in the Torah are opened to interpretation in some way, potentially subject to ruling by the Sanhedrin. And some mitzvot (examples below) seem to require the presence of the Sanhedrin.
In Maimonides' 613 mitzvot list, the presence of a Sanhedrin is required for carrying out some of the mitzvot. Examples:
- The Sanhedrin must count seven groups of seven years Lev. 25:8
- The Sanhedrin must sanctify the fiftieth year Lev. 25:10
- The Sanhedrin must bring an offering when it rules in error Lev 4:13
- Israel must act according to the ruling of the Sanhedrin Deut. 17:11
Here's my question: why isn't there a centralized Sandhedrin today? Now that the exile has ended, is it a matter of broad support in unifying the factions? Do some Jews believe there is no need? Are we waiting for the Beit HaMikdash to be built?
Wikipedia says there has been one significant attempt in recent times (2004) to reinstitute the Sanhedrin, but it doesn't comment much on the ongoing success of said attempt, and website it links to is dead.