Gemara

(Mishnah): If one stole and fed the theft to his children, or left it in front of them, they are exempt. If it was something was Achrayus, they are liable.

(Rav Chisda): If Shimon stole from Reuven, and Reuven did not despair, and Levi ate it, Reuven may collect from either one, whomever he wants.

This is because as long as Reuven did not despair, it belongs to him. (Also Levi stole from Reuven.)

(Mishnah): If he left it intact in front of them, they are exempt.

(Rami bar Chama): This teaches that heirs are like buyers. (They acquire through Shinuy Reshus (change of ownership) after despair.)

(Rava): Heirs are unlike buyers. The case is, they ate the theft.

Question (Seifa): If it was something with Acharayus they are liable.

This implies that in the Reisha, the theft is still around!

Answer (Rava): I explain the Mishnah like R. Oshaya's Beraisa;

(R. Oshaya - Beraisa): If Reuven stole and fed the theft to his children, they are exempt. If he left it intact in front of them, they are liable. If not, they are exempt. If he left them property with Acharayus, they are liable.

Question (middle clause): If the stolen object is not intact, they are exempt. This refutes Rav Chisda!

Answer (Rav Chisda): The Beraisa discusses after despair.

Question (middle clause): If the stolen object is intact, they are liable.

This refutes Rami bar Chama!

Answer (Rami bar Chama): This is before the owner despaired.

Rishonim

Rif and Rosh (10:1): The Mishnah discusses after despair, and the theft is not intact. If the theft is intact, even after despair, they must return it, like R. Oshaya's Beraisa. Nowadays that creditors collect from Metaltelim (of orphans), they must pay from Metaltelim that their father left, whether before or after despair, whether or not they ate it.

Hagahos Ashri: The Ri says that after despair, even though Reuven can collect from Levi due to R. Noson's law (since Levi's creditor owes Reuven), he does not collect due to the law of theft. Some say that if Shimon pardoned Levi or Levi paid Shimon, Levi has no liability to Reuven.

Rosh: They are exempt when the theft is not intact, even though there was no Shinuy Reshus. An heir is unlike a buyer. The same applies when another ate it, since the thief did not sell or give it to him.

Rambam (Hilchos Gezeilah 5:4): If one transgressed and ate theft after despair, he is exempt. If he ate before despair and the owner wants to collect from him, he may, for it is still in the owner's Reshus. If he wants, he may collect from the thief.

Magid Mishneh: Some say that even if the thief fed it to someone, the owner can collect from whom he wants. The Rambam did not distinguish.

Rambam (5): If one stole and died, whether he fed the theft to his children after despair, or did not feed them, rather, sold or lost it, if he left land they must pay. They need not pay from Metaltelim, for the value of the theft is a debt against the thief, and there is no lien on Metaltelim to collect a debt.

Rambam (6): Ge'onim enacted that a creditor collects from Metaltelim, even a Milveh Al Peh. Therefore, they must pay whether or not they ate, whether or not the owner despaired, from land or Metaltelim that the thief left.

Poskim

Shulchan Aruch (CM 361:5): Shinuy Reshus is only if the thief sold or gave it to another.

Source: Beis Yosef DH v'Lo, citing the Ra'avad.

Rebuttal (Gra 2): We say that one who saves from troops or bandits, after despair, acquires (114a). Sukah 30b says that if one cuts myrtle from the Nochri's land, he does not acquire, because land cannot be stolen. This shows that Shinuy Reshus applies against the thief's will!

Amudei Esh (in Sedei Eliyahu): The Gra means that if Shinuy Reshus applies against the thief's will, we understand why it matters that land cannot be stolen, and the myrtle belongs to the original owner until it is cut. But if Shinuy Reshus requires the thief's will, even if land could be stolen, it would not help to cut the myrtle from the land of the Nochri (who stole the land, without the Nochri's permission)!

SMA (5): If the thief sold or gave it, it is Shinuy Reshus even if the recipient knew that it was stolen. This is unlike the Beis Yosef (369:7).

Rema: Some say that if he sold it with Achrayus, or gave it by mistake or Bal Korcho (against his will), it is not Shinuy Reshus.

Shach (3): The Rashba says that through a mistake it is not Shinuy Reshus; the Ba'al ha'Ma'or and Ramban disagree. The Rashba says that Bal Korcho is not Shinuy Reshus; the Rambam and Mechaber disagree.

R. Akiva Eiger: This is when the Achrayus is explicit.

Shach (37:29): The Nimukei Yosef says that if the thief sold it with Achrayus, it is as if it is still in his Reshus, so it is not Shinuy Reshus. I disagree. Achrayus does not affect Shinuy Reshus. The Poskim say that despair and Shinuy Reshus acquire. They did not distinguish whether there was Achrayus.

Shulchan Aruch (ibid): If Shimon stole from Reuven, and Levi took it from Shimon's house against his will, it is as if he took it from Reuven's house.

Gra (6): This is unlike Tosfos (111b DH Gazal), who says that this is Shinuy Reshus.

Shulchan Aruch (ibid): Reuven may collect from either one he wants, or half from each. If Levi paid Shimon, or Shimon pardoned Levi, this does not exempt Levi, for his liability is only to Reuven. It does not matter whether or not Levi knew that Shimon stole it. Even if Levi ate it, he pays Reuven.

Shulchan Aruch (6): This is when Reuven did not despair. If he despaired and then Levi ate it, he is exempt. Even though if it were intact, Levi would need to return it, now that he ate it, he is exempt.

Shulchan Aruch (7): If the thief died and bequeathed the theft to his children, it is as if he is alive. If the theft is intact and unchanged, they must return it even if the owner despaired. If it changed and it is intact, they pay its value. If they ate it before or after the father died, they are liable if it was before despair.

Beis Yosef (DH u'Mah she'Omar): The Poskim rule like Rava, that an heir is unlike a buyer.

SMA (8): An heir is the leg (continuation of) his father. He is unlike a buyer.

Gra (9,11): This Sa'if is like the Tosefta and Tosfos, who obligate Levi even if Shimon fed him. Sa'if 5 connotes like the Ba'al ha'Ma'or, who obligates only Shimon in this case.

Shulchan Aruch (ibid): If they ate after despair they are exempt, unless their father left property. If he left property, even if they ate it after despair they must pay. Likewise, if the father sold or gave it, if he left property his sons must pay.

SMA (10): The father's property was Meshubad from when he stole. The Shulchan Aruch does not distinguish land from Metaltelim, for nowadays even Metaltelim are Meshubad.