The following is a loose translation of notes from lectures by R. Joseph B. Soloveitchik, compiled by R. Elyakim Koenigsberg (whose helpful footnotes are omitted here). It is the first chapter in Shi’urei Ha-Rav on Yoreh De’ah topics (which will be available for sale on the OU website soon, hopefully within a week or two). I post this translation because it is not only worthwhile Torah but also relevant as it sheds light on the issue of whether a woman can become a rabbi. It seems clear to me that if a woman may not be appointed a slaughterer, as the Rema rules, then she may also not be appointed a rabbi.
The Shulchan Arukh (Yoreh De’ah 1:1) writes: “Anyone can slaughter [animals] ab initio, even women.” The Rema adds that we should not allow women to slaughter since the custom is that they do not. This is the view of the Agur brought in the Beis Yosef (ad loc.) that since the custom is that women do not slaughter, therefore they are not allowed to do so because “the custom overrides the law.”
The Beis Yosef already questioned this view: It would be understandable if women had wanted to slaughter but they were never allowed to do it — then we could bring proof from these actions that the custom is that they may not slaughter. But since this is not the case and all we know is that, in practice, women did not slaughter, what is the proof? We say in general that “not seeing is not a proof” — the fact that we have not seen women slaughterers does not necessarily mean that they may not. The Shakh (ad loc., no. 1) answers that perhaps the Agur shares the view of the Maharik, that regarding customs we do say “not seeing is a proof.” Therefore, the fact that we have not seen women slaughteres is sufficient to prove that the custom is that they may not.
Based on this position of the Maharik, we can explain other customs brought down by the Rema. 1) The Rema writes in the laws of mourning (Yoreh De’ah 381:1) that even though the rule is that washing your face, hands and legs in warm water and torso in cold water is only prohibited during the first week of mourning, the custom in his time was to refrain for the entire first thirty days of mourning — “And you should not deviate from the custom because it is ancient and was established by elders.” 2) The Rema (Yoreh De’ah 389:3) also wrote that the rule is that you may not wear Shabbos clothes during the first thirty days of mourning even when mourning for a parent, but the custom is to refrain for the entire twelve months of mourning for a parent.
These two customs are perplexing because how can we establish a custom by refraining from doing something. Don’t we say that “not seeing not a proof”? We have to say that the Rema follows the Maharik, that refraining does not show a tradition regarding a law and certainly does not establish the rule when there is no opinion corresponding to that practice. But it does serve to establish and create a custom that we are obligated to follow.
We can add another reason why we should not allow women to serve as slaughterers. The Rema (Yoreh De’ah 1:1) wrote that we should only rely on the presumption that most people who slaughter are experts post facto, but ab initio we should check someone who comes to slaughter to see if he knows the laws. Because of this, the Rema continues, our practice is not to allow someone to slaughter unless he receives authorization (kabbalah) from a scholar, and the scholar will not give him authorization until he has shown that he knows the laws of slaughtering and how to do it. Since the custom is to receive authorization from a scholar, we do not need to check every person who comes to slaughter because we can assume that most people who come to slaughter have received authorization from a scholar. That is what the Rema wrote.
It seems that since our custom is to receive authorization from a scholar in order to slaughter, therefore slaughtering is no longer merely a matter of permitted or forbidden foodmatter that anyone can do but has become an appointed communal position. For this reason, we do not allow women to slaughter based on the Rambam (Mishneh Torah, Hilkhos Melakhim 1:5), who wrote that we do not appoint a woman to a communal position. Since a woman may not be appointed to a communal position, and slaughtering has become a communal position, therefore it seems that a woman may similarly not be appointed to be a town slaughterer.
We can bring proof to this conclusion from citation of the Beis Yosef from the Kol Bo that women may slaughter animals for their own consumption. The Beis Yosef questions this because what difference is there between slaughtering for others and slaughtering for yourself — a woman has to eat kosher meat like everyone else. The Beis Yosef felt forced to say that the Kol Bo really meant that a woman may slaughter by herself, without anyone standing watch over her. However, based on our idea above, we can explain the Kol Bo simply: Since women may not serve as slaughterers because they may not be appointed to communal positions, it makes sense that they may not slaughter for other people which would be a communal appointment. But they may slaughter for themselves, which is not considered a communal appointment.
The Shulchan Arukh (Yoreh De’ah 1:11) wrote that if a community issued a decree that only one butcher may slaughter but someone else did, his slaughtered meat is forbidden. The Shakh (no. 34) explains in the name of Rabbenu Yerucham that the reason is because he is considered suspect for this matter. However, according to our idea above, even without this reason we would still forbid his slaughtered meat. Since slaughtering is a communal appointment, anyone who is not appointed by the community is excluded from slaughtering and his slaughtering is forbidden.
However, there is a problem with this idea because the Tur wrote that freed slaves are valid slaughterers and it is clear in Yevamos (45b) that a convert may not be appointed to a communal position (see this post: link). Since a freed slave is a convert, how can he slaughter if that is considered a communal position? We have to say that really a convert may be appointed to a communal position, but not a position of communal authority over Jews — and it is for this reason that he may judge a fellow convert (Yevamos 102a). Therefore, since slaughtering is not a position of authority, a convert may be appointed to be a slaughterer. However, a woman is excluded from all appointments, even those with no authority, and therefore she may not be appointed a slaughterer.