If a beis din can be comprised of three 'Hedyotim' and the gemorah does not mention they have the right to refuse permision, or the need to say 'Mutar Lach', Why are they needed? Is it a special heter like Pruzbal?
zvi koff, Brooklyn ny
I presume you mean the Beis Din of Hashavas Aveidah. Rashi (32a DH Im Yesh) learns that we need a Beis Din to be Mafkir the money of the person that lost the article, in order to pay the finder.
See Chochmas Shlomo (from Rav Shlomo Kluger, printed in the Shulchan Aruch, CM 365:1) that this Beis Din must be of Mumchin, or at least one learned person (Gamir v'Savir).
If you are asking something else please let me know.