Gemara

(Mishnah): If a thief stole Shimon's animal and gave it to a Shomer, and he was dragging it out, and it died in Shimon's premises, he is exempt. If he lifted it, or took it outside and then it died, he is liable.

(Rav Yeimar): Reuven's Shomer was dragging it. (Reuven is exempt because Meshichah is not complete until it leaves the owner's premises.)

Kidushin 42b (Beraisa): If Reuven sent Shimon to buy something, and he gave to him Hekdesh money, if he fulfilled his mission, Reuven transgressed Me'ilah.

Normally, Ein Shali'ach l'Devar Aveirah. A Gezeirah Shavah "Chet-Chet" teaches that just like one can make a Shali'ach for Terumah, also for Me'ilah.

43a: If a thief stole a sheep, goat or ox, and slaughtered or sold it, he pays four or five times its value, even if he sold or slaughtered through a Shali'ach.

(Beraisa): If Levi made Shimon a Shali'ach to kill someone (and he did), Shimon is liable, and Levi is exempt;

Shamai obligates Levi - "you (David) killed him (Uriyah) with the sword of Amon".

Shamai holds that Yesh Shali'ach l'Devar Aveirah. Or, Ein Shali'ach; Levi is liable b'Yedei Shamayim (the first Tana obligates him less). Or, Shamai learns from "you killed...." that Yesh Shali'ach for murder. The first Tana holds that the verse teaches that David is exempt, for Uriyah rebelled against the king.

Bava Metzia 10b: R. Yochanan holds that the Torah says that a Chatzer acquires like one's hand. Reish Lakish holds that it acquires like one's Shali'ach.

Question (against Reish Lakish): A Beraisa obligates a thief if the stolen object is found in his Chatzer. We hold that Ein Shali'ach l'Devar Aveirah!

Answer #1 (Ravina): Ein Shali'ach l'Devar Aveirah only when the Shali'ach is Bar Chiyuva (liable for transgressing).

Answer #2 (Rav Sama): Ein Shali'ach l'Devar Aveirah only when the Shali'ach can choose whether or not to comply.

They argue about a Kohen who told a Yisrael 'be Mekadesh a divorcee to me', or a man who told a woman 'cut a boy's sideburns for me.' Rav Sama exempts the Meshale'ach, and Ravina obligates him.

Rishonim

Rif and Rosh (Kidushin 16b and 2:2): Actions of David's Shali'ach are attributed to David, unless he was told to do an Aveirah. Then, we say that he should have listened to Hash-m, not to David.

Rambam (Hilchos Me'ilah 7:1): If Reuven told Shimon "give one piece of meat to each guest," and Shimon told the guests 'I allow you to take two each', and the guests took three each (and the meat was found to be Hekdesh), all were Mo'el.

Rambam (2): This refers to meat of Bedek ha'Bayis. If the meat was of an Olah, only the ones who ate transgressed Me'ilah, for there was another Isur in addition to Me'ilah. In the entire Torah, Ein Shali'ach l'Devar Aveirah, except for Me'ilah with no other Isur involved.

Noda bi'Yehudah (EH 80 DH u'Milvad and 75 DH v'Af): Ein Shali'ach even when the Shali'ach was Shogeg. Here they were all Shogeg (Me'ilah is only b'Shogeg), yet Ein Shali'ach if another Isur was involved! Also, Rava taught about Yesh Shali'ach for eating Chelev according to Shamai (Kidushin 43a). If Yesh Shali'ach b'Shogeg, he would have taught according to Halachah!

Rosh (Bava Metzia 1:30): The Ramah says that the Halachah follows Rav Sama Therefore, the only Shali'ach l'Devar Aveirah is a Chatzer.

Question: Why is the thief liable due to the Shomer's Meshichah (Bava Kama 79a)? Ein Shali'ach l'Devar Aveirah!

Answer #1 (Tosfos Bava Kama 79a DH Nasno): The Shomer thinks that it is the thief's. Yesh Shali'ach when the Shali'ach is not Bar Chiyuva, or has no choice, for the Meshale'ach does not expect the Shali'ach to obey. If the Shali'ach thinks that it is the thief's, the thief expects him to obey!

Answer #2 (Nimukei Yosef Bava Kama 29a DH Masnisin (2)): The Acharonim disagree. In Bava Metzia, we asked why a Chatzer can be a Shali'ach l'Devar Aveirah, even though it has no Da'as! David was not punished for killing Uriyah, because Ein Shali'ach, even though Yo'av was Shogeg (he thought that Uriyah was Chayav Misah)! Rather, if the Shomer took it out, the Shomer is liable (for its death) to the owner, like we find in Bava Metzia (35b).

Rebuttal (Yam Shel Shlomo): Yo'av knew that Uriyah was not Chayav Misah, for David commanded to kill him subtly (to put him at the front lines, and withdraw from him). The Tana who argues with Shamai obligates a Shali'ach who kills. They discuss a case like this, for they argue about the verse! Yo'av erred by not expounding Mi'utim (not to obey a king's order to transgress - Sanhedrin 49a). In Kidushin, we conclude that Uriyah was Chayav Misah for rebelling against the king, unlike Sanhedrin 49a. Tosfos said that Yesh Shali'ach when the Shali'ach is Shogeg, and had no question about this.

Rebuttal (Shach CM 348:6): Ravina says that Yesh Shali'ach when the Shali'ach is not Bar Chiyuva, i.e. the Isur never applies to him (not that he is exempt for he was Shogeg). Also, he can choose whether or not to do it even if he is Shogeg! Rashi obligates the thief due to the Shomer's Meshichah. This is wrong. If so, why did we challenge Reish Lakish from a Beraisa (Bava Metzia 10b)? We can challenge even R. Yochanan from the Mishnah; and the answer suffices for Reish Lakish! Rather, we must explain the Mishnah like the Nimukei Yosef or others. There is no source to say Yesh Shali'ach when the Shali'ach is Shogeg. Yo'av assumed that David had a valid reason to kill Uriyah covertly. We derived that Shamai holds that Yesh Shali'ach since he says that David was liable, even though Yo'av was Shogeg!

Tosfos (Kidushin 42b DH Amai): Me'ilah is only b'Shogeg. If so, surely Yesh Shali'ach, for the Shali'ach had no reason not to do like he was told! We ask why the Meshale'ach was Mo'el when he was Shogeg and the Shali'ach was Mezid.

Question (Tosfos, ibid.): How did we try to learn Shali'ach l'Devar Aveirah from selling a stolen animal (which is always through someone else)? Perhaps this is when the seller does not know that it is stolen!

Answer (Yam Shel Shlomo Bava Kama 7:33): The Torah equates selling and Shechitah. Just like a thief is liable for selling via (i.e. to) another, even if he knows that it is stolen, he is liable for slaughter through another who knows.

Rebuttal (Shach CM 348:6): Since this opinion does not expound anything extra in the verse, we should learn the smallest Chidush, when the other person is Shogeg! Rather, even b'Shogeg, Ein Shali'ach.

Poskim

Rema (CM 182:1): In all matters, actions of David's Shali'ach are attributed to David, except for an Aveirah. We hold that Ein Shali'ach l'Devar Aveirah, when the Shali'ach is a Bar Chiyuva. If he is not, he is a Shali'ach even for an Aveirah.

Darchei Moshe (CM 348:3 DH v'Chosav Mordechai): The Mordechai (Bava Metzia 237) obligates the Meshale'ach when the Shali'ach is exempt. If David told Levi 'take my ox from Ploni's house', and it was found that David intended to steal it, he is liable through Levi's Meshichah, for Levi did not know that it is stolen. The Nimukei Yosef obligates the Shali'ach, for Ein Shali'ach even when the Shali'ach does not know that it is forbidden.

Rebuttal (Shach 6): The Nimukei Yosef exempted the Meshale'ach. There is no reason to obligate the Shali'ach! The Yam Shel Shlomo says so explicitly.

Rema (348:8): If a thief hid a stolen object and needed to leave the city before he was able to take it, and he sent Levi to bring it, Levi must pay. He is the primary thief, since he knew that it is stolen.

Gra (27): If Levi did not know, he is exempt and the Meshale'ach is liable.