Gemara

The Beis Din of Tiverya sent to Mar Ukva (in Bavel): Ukvan (of Bavel) claims that his brother Yirmeyah castrated him (some say - cheated him). Tell (Yirmeyah) to come to you for judgment, and force him be judged in Tiverya.

(Rav Ashi): It was a case of a fine. Mar Ukva could not judge it in Bavel. They sent to him to show honor to him.

Bava Kama 15b: Since half-damage is a fine, if a dog killed and ate sheep, this is abnormal (a Toldah of Keren), so we do not collect it in Bavel. If the victim seized payment, we do not make him return it. If the victim requested to fix a time to go to Eretz Yisrael to judge the case, we comply. If the damager does not agree, we excommunicate him.

84b (Rava): If a man or ox damaged an ox, we collect this in Bavel. If a man or ox damaged a man, we do not collect this in Bavel.

Question: We don't collect damages to a man, for it says "Elohim", i.e. judges with Semichah. Also regarding damages to an ox, it says "Elohim"!

Answer: We (judges in Chutz la'Aretz) are Sheluchim of ordained judges in Eretz Yisrael to collect damages to an ox, just like we are Sheluchim to judge cases of admissions and loans.

Question: We should be Sheluchim also for damages to man!

Answer: We are Sheluchim only for common cases in which the victim loses money. It is not common for a man to hit a man. Embarrassment is common, but the victim does not lose money.

Contradiction: Rava said (Sof 84a) that we collect for an ox that damages an ox, and he said that we do not collect damage due to an ox in Bavel.

If it struck a man, Rava should have taught that we do not collect even for a man who struck a man! Rather, it struck an ox, and Rava taught that we do not collect!

Answer #1: We do not collect from a Tam. We collect from a Mu'ad.

Objection: Rava taught that (becoming) Mu'ad does not apply in Bavel!

Answer #2: Regarding Shen and Regel, which are Mu'ad from the beginning, Rava taught that we collect for an ox that damaged an ox.

Gitin 88b: Rav Yosef was forcing a man to give a Get.

Question (Abaye): We (Chachamim of Bavel) are like commoners. We cannot coerce to divorce!

(Beraisa - R. Meir): "These are the judgments that you will put before them" (expert judges)", and not before commoners.

Answer (Rav Yosef): We are Sheluchim of the experts in Eretz Yisrael (for Gitin), just like we are their Sheluchim for admissions and loans.

Question: If so, we should be Sheluchim also for thefts and injuries!

Answer: We are Sheluchim only for admissions and loans, for these are frequent.

Rishonim

Rif and Rosh (Bava Kama 30a and 7:2): If a man or ox damaged an ox, we collect this in Bavel, but not if a man or ox damaged a man, for it says "Elohim". Judges in Chutz la'Aretz are Sheluchim of Semuchim in Eretz Yisrael to collect damages to an ox, just like they are Sheluchim for admissions and loans. We are Sheluchim only for common cases in which the victim loses money. It is not common for a man to hit a man. Embarrassment is common, but the victim does not lose money. If an ox damaged an ox through Shen and Regel, which are Mu'ad from the beginning, we collect for it. The custom of two Yeshivos is that even though we do not collect fines in Bavel, we excommunicate him until he appeases his opponent. Once he gives the proper amount, we permit the Niduy whether or not the victim was appeased.

Rosh: This custom of the Yeshivos is an enactment. Excommunication until one pays is the ultimate coercion. The Gemara says that we excommunicate until he removes the damager, but not until he pays! Mar Tzemach Gaon was asked if they should collect for rape or enticement in Bavel, lest a sinner profit. He answered that the rule is that we do not collect fines in Bavel. However, we do not want sinners to profit and Yisre'elim to wantonly harm others. Therefore, latter Chachamim excommunicate until the victim is appeased through money, or verbally through bringing friends. A case occurred in which Reuven knocked out Shimon's tooth. Rav Tzadok Gaon excommunicated him. He did not fix an amount, but told him to appease him. The custom is like this. Rav Shrirah Gaon says that this is because Chachamim saw bad results from not collecting fines. We do not fix an amount needed to appease, for this is like collecting a fine. Rather, we estimate what is proper, but do not reveal it. If he gives close to this and the victim is not appeased, we end the Niduy. If he gave much less, we do not permit the Niduy until he gives close to the assessment.

Rambam (Hilchos Sanhedrin 5:8): Fines such as thefts, wounding, payment of Kefel, four or five... are imposed only by expert judges, i.e. who received Semichah in Eretz Yisrael. Three commoners, and even one expert suffice for other monetary laws such as admissions and loans. Therefore, we judge them in Chutz la'Aretz. Beis Din in Chutz la'Aretz is not called 'Elokim'; they are Shluchim of the Beis Din in Eretz Yisrael, but not to judge fines.

Rambam (9): Judges in Chutz la'Aretz collect only common matters in which a party loses money. They do not collect for an animal that damaged another or wounded another. They do not collect half-damage, except for damage of pebbles, which is Mamon, not a fine.

Or Some'ach (Hilchos Nizkei Mamon 2:9): It is unusual for a dog to kill sheep, so paying for the loss due to death is a fine. However, it is normal to eat the meat, so one pays fully for this (even in Bavel).

Rosh (Sanhedrin 1:1): The Gemara (32b) says that fines require interrogation. This is not limited to fines. The Gemara calls 'fines' anything that requires Mumchim. The Gemara (14a) says that fines would have been Batel, and it refers to everything that requires Mumchim. The conclusion in Bava Kama (84b) is that judges in Bavel are Sheluchim for everything common, just like admissions and loans. It says that wounds are not common. This implies that everything else, including theft, is common. Therefore, (in Bavel) we judge everything except for wounds. We do not need Mumchim, nor interrogation.

Tosfos (Gitin 88b DH b'Milsa): Nowadays we accept converts in Chutz la'Aretz, even though three experts are required. This is common, so we are Shluchim of Semuchim in Eretz Yisrael. Nowadays there are no Semuchim in Eretz Yisrael. We are Shluchum of Senuchim of previous generations.

Poskim

Shulchan Aruch (CM 1:1): Nowadays judges judge admissions and loans, Kesuvos, inheritance, gifts and damaging another's property. These occur constantly, and a party loses money. Only experts with Semichah in Eretz Yisrael judge rare matters, even if there is loss of money, e.g. an animal that damaged another animal, or matters without loss of money, even if they arise constantly, such as Kefel or fines that Chachamim imposed, e.g. for slapping someone.

Shulchan Aruch (5): Judges without Semichah in Eretz Yisrael do not collect fines, but they excommunicate until he appeases the victim. Once he gives the right amount, we permit the Niduy (even if the victim was not appeased). Similarly, if the victim seized the proper amount, we do not make him return it.

Rema: If the victim says 'assess the damage so I will know how much I may seize', we do not comply. If he already seized, we assess and say 'keep this much, and return the rest.' This refers to fines that were written. Fines that Chachamim themselves make for their enactments are collected everywhere.

Shulchan Aruch (6): If one embarrassed verbally, we excommunicate him until he properly appeases the victim according to his honor.

Tur: If an animal damaged an animal through Keren (goring) or its derivatives, we do not collect this in Bavel. We hold that half-damage of a Tam is a fine, which we do not judge in Chutz la'Aretz. We do not make an animal Mu'ad in Bavel. Even if it became Mu'ad in Eretz Yisrael and went to Bavel, we do not judge it, for it is not common.

Beis Yosef (DH u'Mah she'Chosav v'Chen, based on Rashi Bava Kama 84b DH Ein): Since we do not collect for a Tam that gored, it cannot become Mu'ad.

Rejection (Tosfos Rid Bava Kama 84b DH v'Ha): We do not collect from a Tam of a Cheresh, lunatic or child, yet we testify in front of an Apotropos in order to make it Mu'ad. We could do similarly for a Tam in Bavel! Rather, testimony to make a Mu'ad must be in front of judges with Semichah, which we lack in Bavel.