10. If someone doesn't know who declared the Nidui on him, he may go to the Nasi (head of the Court), who will lift the ban.

Q1: May the Nasi lift the ban even if the Menudeh knows who banned him, but doesn't want to go to him? Or that person (as in the previous Halakha) left town?

YE: From the sugya in Mo'ed Kattan (17a), it seems that the Nasi may only operate in this way when the Menudeh cannot identify the one who placed him in Nidui. It does not necessarily follow that if the person was known but unavailable or died, that the Nasi may lift the ban - that may require a regular Beit-Din (as in MT Talmud Torah 6:12).

Q2: What is the function of the Nasi here - as representative of the court or it's highest officer?

YE: Since we learned that if the Nasi declares Nidui, all Jews mujst respect it - but not the inverse - (MT Talmud Torah 6:13) - it follows that it is the Nasi's office which stands on top of the "Nidui hierarchy" - due to the Beit-Din and Torah-honor nature of Nidui (as mentioned above). Here, the Nasi may lift the ban because he is the highest officer of the court. Since the hierarchy of the court climaxes with the Nasi, any Nidui-related issue will become subject to his approval or lack thereof.

Rambam, Copyright (c) 1999 Project Genesis, Inc.