1) THE "BITUL" OF A "TZEDUKI"
QUESTION: The Gemara points out an apparent contradiction between the opinion of Rebbi Yehudah as expressed in the Mishnah (61b) and his opinion as expressed in the Beraisa (68b). In the Mishnah, Rebbi Yehudah states that a Tzeduki is able to be Mevatel his Reshus to the other residents of the Chatzer. In the Beraisa, however, Rebbi Yehudah states that a Tzeduki's Bitul is not effective at all.
The Gemara gives two possible ways to reconcile the contradiction. First, the Gemara suggests a different interpretation of the statement of Rebbi Yehudah in the Mishnah, so that it reads like his statement in the Beraisa (and he does not permit the Bitul of a Tzeduki at all). Second, the Gemara suggests that Rebbi Yehudah in the Mishnah refers to a Tzeduki who desecrates Shabbos only in private, whose Bitul is valid, while in the Beraisa he refers to a Tzeduki who desecrates Shabbos in public, whose Bitul is not valid. According to Rebbi Yehudah, a Tzeduki who desecrates Shabbos only in private may be Mevatel Reshus to the Jews in the Chatzer, and a Tzeduki who desecrates Shabbos in public may not be Mevatel Reshus. (The Rabanan did not permit the residents of a Chatzer to rely on the Bitul of one who publicly desecrates Shabbos, because they did not want Jews to live near such a person, lest they be tempted to emulate his sinful deeds. In this respect, such a Jew has the status of a non-Jew.)
RASHI (61b, DH Maharu), in his explanation of the Mishnah, says that one may not rely on the Bitul of the Tzeduki because the Tzeduki might carry from his house to the Chatzer and annul the Bitul at any moment. That is, the Bitul of a Tzeduki is technically valid, but the Rabanan invalidated it out of concern that he would retract it.
Rashi's explanation is difficult to understand, because the Gemara does not entertain the possibility that the Tzeduki's Bitul is inherently valid but the Rabanan invalidated it. The Gemara's only possibilities are that Rebbi Yehudah either does not allow the Bitul of a Tzeduki at all, or that he allows it entirely because the Tzeduki desecrates Shabbos only in private! (TOSFOS REBBI AKIVA EIGER on the Mishnah, RASHASH)
ANSWER: Perhaps Rashi's explanation of the Mishnah reflects the way he understands the first answer of the Gemara. Rashi understands that the Tzeduki's Bitul is inherently valid. However, we may not rely on that Bitul to permit one to carry in the Chatzer, because the Tzeduki is able to rescind his Bitul at any moment (and, according to Rebbi Yehudah, it does not help for the Jews to make a Chazakah in the Chatzer). As a result, the Rabanan did not permit us to rely on his Bitul, lest he revoke it at some point during Shabbos.
What, though, is Rashi's source to interpret the Gemara's answer this way? The straightforward reading of the Gemara suggests that Rebbi Yehudah does not allow the Bitul of a Tzeduki in the first place!
Perhaps Rashi had a slightly different text in the Mishnah. Indeed, we find that when Rashi on the Rif (beginning of page 21a of the pages of the Rif) quotes the Mishnah, he uses the words "Shema Yotzi" in place of "Ad she'Lo Yotzi." The words "Shema Yotzi" clearly indicate that the Jews may not rely on the Tzeduki's Bitul lest he revoke it. According to Rashi, this is also the intention of the Gemara when it says that Rebbi Yehudah means "Ad she'Lo Yetzei ha'Yom." (In the Saloniki edition of the Shas, this explanation is even more evident. The Mishnah says that according to Rebbi Yehudah, the instructions were, "Quickly take care of your needs in the Mavoy mib'Od Yom, before the Tzeduki carries from his house to the Chatzer and thereby prohibits carrying in the Mavoy.") (M. KORNFELD)
2) HALACHAH: A JEW WHO DOES NOT OBSERVE MITZVOS
OPINIONS: The Gemara says that according to Rebbi Yehudah, a Tzeduki who desecrates Shabbos only in private may be Mevatel his Reshus to the Jews in the Chatzer. A Tzeduki who desecrates Shabbos in public may not be Mevatel his Reshus. Raban Gamliel disagrees and rules that a Tzeduki's Bitul is always valid. Raban Gamliel does not differentiate between one who privately desecrates Shabbos and one who publicly desecrates Shabbos.
The Gemara cites a Beraisa which adds that an ordinary Jew (not necessarily a Tzeduki) who desecrates Shabbos in public may not be Mevatel his Reshus. The Gemara says that this Beraisa follows the view of Rebbi Yehudah.
Whom does the Halachah follow?
(a) The MORDECHAI and MAHARAM MI'ROTENBURG (cited by the Rosh) rule like Rebbi Yehudah that a Tzeduki who desecrates Shabbos in public is like a non-Jew and may not be Mevatel his Reshus to enable the other residents in the Chatzer to carry there on Shabbos.
(b) The ROSH (6:13) rules like Raban Gamliel that a Tzeduki may be Mevatel his Reshus, even if he desecrates Shabbos in public.
HALACHAH: There are various opinions regarding the practical Halachah.
(a) The SHULCHAN ARUCH (OC 385:1) rules that a Tzeduki's Bitul is valid even if he desecrates Shabbos in public (see also BEIS YOSEF), as the Rosh says. However, the Shulchan Aruch (385:3) also rules that a Jew who desecrates Shabbos in public may not be Mevatel his Reshus, and he bases this ruling as well on the Rosh (6:14).
It seems that the Rosh understood the dispute between Raban Gamliel and Rebbi Yehudah to involve only a Tzeduki. They both agree, though, that an ordinary Jew who went astray and desecrates Shabbos in public may not be Mevatel Reshus. What is the difference between a Tzeduki and an ordinary Jew who went astray?
The Beis Yosef says that the difference is that a Tzeduki was raised by his parents to believe that his way of life is the true Torah way. He does not transgress the Torah out of heresy, but out of habit. Therefore, he is not considered a non-Jew with regard to Bitul. A "Mumar," in contrast, has made a conscious decision to transgress the Torah, and therefore he has the status of a non-Jew with regard to Bitul.
(b) The MISHNAH BERURAH (Sha'ar ha'Tziyun 385:2) questions the ruling of the Shulchan Aruch and the words of the Beis Yosef. First, he asks that the Beis Yosef says that the RAMBAM (Hilchos Eruvin 2:16) also makes this distinction, allowing Bitul by a Tzeduki but not by a Jew who desecrates Shabbos in public. However, the Rambam clearly states there that a Tzeduki's Bitul is valid because a Tzeduki does not desecrate Shabbos!
Second, even if we are lenient with regard to a Tzeduki because he was raised to believe that he is abiding by the Torah, that consideration is not relevant to the laws of Eruv Chatzeros. The reason why a heretic's or non-Jew's Bitul is not valid is because the Rabanan did not want Jews to live near those people, and thus they made it difficult to permit carrying in a Chatzer shared with such neighbors. This Gezeirah should also apply to a Tzeduki's Bitul! Even though he transgresses out of habit, his Bitul should not be valid because we do not want Jews to live near him and learn from his sinful ways!
The Mishnah Berurah (OC 385:1) implies that we should be stringent with regard to a Chatzer shared with a Karaite (a modern form of Tzeduki) who desecrates Shabbos in public, and we should not rely on his Bitul but instead rent his rights from him.
(c) The CHAZON ISH (87:12) defends the position of the Beis Yosef. He explains that the Beis Yosef applies the reasoning that the Tzeduki was raised with his beliefs only to a Tzeduki in modern times, who transgresses only out of ignorance and not out of a genuine belief that his way is the true way. There is no fear that other Jews will learn from his ways, because when he is informed that he is wrong, he will correct his ways!
Based on this explanation, the Chazon Ish (87:14) rules like the Beis Yosef that a Jew who was not raised to be observant of Torah and Mitzvos and is ignorant of the laws (and who presumably does not intentionally transgress) is not only considered a Jew with regard to Bitul, but one may transfer to him a share in the Eruv Chatzeros. (RAV MOSHE STERNBUCH shlit'a takes issue with the ruling of the Chazon Ish; see Teshuvos v'Hanhagos 1:252.)