Responsa על בבא מציעא 225:11

Q. A deposited money with B. Subsequently, C seized this money in payment of the money B owed him. B admits that the money belongs to A. Now A demands it from C.
A. Since B admits that the money belongs to A, C must return it to the latter. The fact that B is responsible for A's deposit and would have to compensate him for its loss, does not make B the owner of the deposited money. Thus the Talmud (B.K. 115a) rules that a creditor who received, from a thief, stolen goods in payment of his debt must return the goods to its original owner.
This Responsum was addressed to Rabbi Asher who took exception to R. Meir's derivation of the law by conclusion ad majus, arguing that our case cannot be compared to that of a thief who repaid his debt with stolen goods, for a thief has acquired his ill-gotten gain sinfully and those who received the goods from him are dealt with severely; but C committed no sin in seizing A's money since "a person may execute judgment on his own behalf" (B.K. 27b). R. Meir, however, pointed out that C also committed a sin in seizing the property of another, for the talmudic dictum "a person may execute judgment on his own behalf" merely means that a person may retrieve his own valuables which he finds in the hands of others; but a creditor is not permitted to seize the valuables of his debtor without a court order.
SOURCES: Cr. 26–7; Mord. B. K. 170; ibid. B. M. 438; Hag. Maim., Nahalot 11, 2; Asher, Responsa 107, 1.

A owed money to B and refused to pay his debt. The Rabbis of Spiers, basing their decision on the statement of R. Nahman (B. K. 27b) that a man is permitted to take the law into his own hands, gave B permission to break into A's house and forcefully take possession of A's valuables in payment of the debt.
R. Meir wrote to the Rabbis of Spiers not to ascribe legal absurdities to R. Nahman; for such interpretation of the words of R. Nahman was not only in opposition to an explicit statement of the Mishna (B. M. 9, 13) but was even against the very words of the Pentateuch (Deut. 24,10). A person is permitted according to R. Nahman, to enter into another person's house and take away an object definitely known to be his own, but he is not permitted to touch an object belonging to the other person, unless accompanied by a law-court official.
SOURCES: Cr. 102; Pr. 950; L. 148; cf. Tesh. Maim. to Nezikin, 14; Beth Joseph to Hoshen Mishpat 388.

Q. A had Gentiles arrest his opponents. One of his opponents resisted arrest; he fled, but was pursued and killed by the Gentiles. A claims that he merely intended to coerce his opponents into answering his summons to court.
A. A is fully responsible for the murder of his opponent, for when a Jew falls into the clutches of Gentiles, his life as well as his property is in jeopardy; he can expect from them neither pity, mercy, nor restraint. The Gentiles are happy to hold a Jew in their power; and, especially when commissioned by another Jew, their cruelty is boundless. They consider it entirely legitimate and even praiseworthy to rob, maim, and even murder a Jew. Therefore, a person who delivers a fellow Jew into the hands of Gentiles is directly responsible for all their cruelties. Thus A is to be considered as much a murderer as if he killed his opponent with his own hands. No punishment is too great for him, no penance too harsh, and no manner of self-torture too severe. Let him be flogged and publicly disgraced, let him wander as an exile in foreign lands, let his face become black through fasting and self-torture for a year or two, and seek atonement for his crime. I subscribe to any punishment you may impose upon him, no matter how severe; and I would agree to still sterner measures but not to milder ones.
SOURCES: Cr. 214; Mordecai Hagadol, p. 248, margin; Hayyim Or Zarua, Responsa 141; cf. ibid. 25; Mahril, Responsa 86; Weil, Responsa 28; ibid. 111, ibid. 147; Menahem of Merseburg, Nimmukim (61).