How can Sumchos argue on a Halachah Lemoshe Misinai and say that tzeroros obligates one to a full payment. Furthermore, if Sumchos says that "Koach Kocho" is the real Halachah Lemoshe Misinai, how is it that Sumchos had a different Masorah of these halachot than the other Amoraim? Are there different traditions on Halachot Lemoshe Misinai?
Mark Staum, Teaneck, New Jersey
(a) Regarding whether it is possible to have a Machlokes concerning a Halachah l'Moshe mi'Sinai, it is well-known what the RAMBAM writes in his introduction to Perush ha'Mishnayos, and in Hilchos Mamrim 1:3, that whatever was received through tradition as a Halachah l'Moshe mi'Sinai will never be the subject of a Machlokes. This is also the implication of Tosfos in Yevamos (77b, DH Halachah; see also Tosfos Yom Tov to Temurah 3:3, DH Temuras Asham).
However, the Rambam himself (in his introduction there) composes a list of "most and perhaps all" of the Halachos l'Moshe mi'Sinai mentioned in Shas, which includes but 22 Halachos -- and the Halachah of Tzeroros is not one of them.
The CHAVOS YA'IR (Teshuvah #192) discusses at length whether a Halachah l'Moshe mi'Sinai can be debated. He lists 75 Halachos l'Moshe mi'Sinai (including the Halachah of Tzeroros), and asks why the Rambam did not mention the other Halachos l'Moshe mi'Sinai. Moreover, we indeed find a Machlokes Tana'im involved with most of the Halachos l'Moshe mi'Sinai that he cites. The Chavos Ya'ir concludes that the Rambam holds that not every Halachah for which the Gemara uses the term, "Gamra Gemiri Lah," is actually a Halachah l'Moshe mi'Sinai. (He goes on to prove this at length from a number of Sugyos.)
He also infers this from the words of the Rambam in Mishneh Torah, who does not mention explicitly the words, "Halachah l'Moshe mi'Sinai," except with regard to the 22 Halachos that he lists in his introduction. For the other Halachos (including the Halachah of Tzeroros), he writes either "Halachah mi'Pi ha'Kabalah" (such as for Tzeroros, in Hilchos Nizkei Mamon 2:1), or "mi'Pi ha'Shemu'ah," or "Nitan la'Hem mi'Sinai," or "mi'Pi Moshe Rabeinu Nishme'u." (See Chavos Ya'ir there, #192:6, 24, 25.) Accordingly, we cannot ask a question on the Rambam's assertion from the argument of the Tana'im regarding the Halachah of Tzeroros.
(b) In addition, the Chavos Ya'ir there (#6) proves from many places that even according to the Rambam, there can be a Machlokes regarding the details of a Halachah l'Moshe mi'Sinai. It is only the general Halachah which is not subject to Machlokes. Hence, according to the opinion that holds that Sumchus also agrees with regard to "Ko'ach Kocho," as you mentioned in your question, there is certainly no question as to how an argument can evolve in the details of a Halachah l'Moshe mi'Sinai.
(c) However, the Chavos Ya'ir there points out that, apparently, not everyone agrees with the words of the Rambam. Tosfos in Eruvin (21b, DH Mipnei) clearly implies that it is possible for a Halachah l'Moshe mi'Sinai to be forgotten, and thus it is possible for it to be subject to Machlokes (in contrast to what the Rambam writes, that it is not possible for a Halachah l'Moshe mi'Sinai to be forgotten). This is also the Chavos Ya'ir's own conclusion, which he bases on numerous sources in the Gemara and on logical arguments. (One of his proofs is from the Halachah of Tzeroros -- HLM #27 in his list -- as you asked.)