The gemara says on daf 18b that a melech is not allowed to serve on an ibur shana beis din because of a bias towars his army. My question is that the mishna says befeirush that a melech is not dan - which means he can't serve on a beis din. So why does the gemara have to come on to a reason of bias of supporting his army. Without that he is always ineligible to serve on a beis din?
Sendy G., Elizabeth, NJ
The Gemara later 19a writes that Malchei Beis David can judge.
However, the Meiri nevertheless asks your question, since those who are Me'aber Shanah must be members of the Sanhedrin and a king, even from Beis David, cannot be a member of the Sanhedrin (since no one is able to argue with him). How then can he be Me'aber the Shanah?
The MEIRI and TESHUVOS HA'RASHBA (6:190) answer that if a person was a Chacham Muflag, he could be from the Mezumanim for Ibur Shana even if he was not from Sanhedrin.
D. Zupnik