Semicha: Then and Now by Rabbi Hershel Schachter

 https://download.yutorah.org/2014/1053/817656/semikhah-then-and-now.pdf

The institution of semicha was introduced to the Jewish people when Hashem commanded Moshe to designate Yehoshua as his successor by placing his hands on his disciple’s head (Bamidbar 27:23). The Gemara (Sanhedrin 13b) comments that from that time on, semicha is no longer given in this manner, but rather through a declaration, by a teacher calling his student “rebbe” and giving him permission to impose fines ordained by the Torah. That same passage also informs us that we no longer have the concept of genuine semicha in our days. The transmission of semicha must be done by someone who himself received semicha through a continuous chain dating back to Moshe Rabbeinu. At some point in history, this chain was interrupted. Though we no longer have this genuine semicha, both its original characteristics and its absence have ramifications for us today.  

On a more practical level, how does the absence of genuine semicha manifest itself in our time? The answer depends on how we determine which situations actually require a rabbi with semicha to decide. This discussion seems to revolve around a disagreement between Tosfos and the Rambam. Tosfos (Yevamos 47a) appear to assume that semicha is a requirement for membership on a beis din. Any time a beis din is needed to rule on a case, only individuals with  semicha can sit on the beis din. The Rambam disagrees and rules that semicha is not a requirement for the beis din. Rather, any hora’ah, or halachic decision, can only be made by one who has received semicha. Let us consider some cases in which this disagreement is relevant.

If we don’t have genuine semicha, what is the purpose of the semicha that is issued nowadays? Even though we no longer confer the original semicha, we may still fulfill Rebbe's institution(Sanhedrin 5b) that one cannot issue rulings (or for the Rambam, even recommendations) without asking permission from his rebbe first. When a rebbe feels that his student is qualified to give halachic advice, he will give the student permission to do so. Semicha today authorizes new musmachim to respond to halachic questions. Its purpose is more to adhere to the statement of Rebbe than a commemoration of what semicha used to be

Finally, the Mishna (Sanhedrin 86b) states that the punishment of a zaken mamre (one who rules against the Beis Din Hagadol) does not apply to a "talmid." Rashi explains that a talmid cannot be a zaken mamre because zaken mamre is someone who issues a formal hora’ah against the Beis Din Hagadol. Yet in defining a talmid, Rashi writes that a talmid is someone under the age of forty. At that age, one is not old enough to issue a hora’ah and therefore one is not considered worthy of hora’ah. The Rambam, however, (Mamrim 3:5) has a different definition of who is worthy of hora’ah. For these purposes, it is one who has semicha. This would appear to be based on the Rambam's understanding that a hora’ah requires one with semicha. If the individual who rules against the Beis Din Hagadol does not have semicha, then his decision is not classified as hora’ah. Any ruling that this individual issues would be considered good advice or a recommendation as to where to look for further guidance, but not a binding halachic statement.