Fact: There is no such ban, and nikkur was practiced in many Ashkenazic communities into the twentieth century. The practice of some communities to refrain from eating hindquarters, owing to the difficulty in excising the forbidden sections, continues to exist among both Ashkenazim and Sephardim.
Background: After a kosher animal is properly slaughtered and inspected, it still may not be consumed until certain large blood vessels, chailev (prohibited fats known as tallow or suet; see, e.g., Vayikra 7:25) and the gid hanasheh (the sciatic nerve) are removed. The removal process is called nikkur (traibering in Yiddish, porging in English), and the person who does it is called a menakker (or treiberer or porger). Other animal parts must also be removed because of their proximity to, contact with, dependence upon or similarity to chailev. This includes permitted fats (shuman) that may be confused with chailev. Nikkur in the forequarters is significantly easier, because the gid hanasheh is located in the animal’s hindquarters. Additionally, the front half of the animal, from rib twelve onward, has almost no chailev. Thus, the primary task in nikkur of the forequarters is removing several blood vessels. (In this article, except where indicated otherwise, nikkur refers to removing the forbidden parts of the hindquarters, not the forequarters.)
The prohibitions involved are indeed serious. Consuming prohibited fats or blood is more serious than eating pork and incurs the severe punishment of karet, while eating the gid hanasheh incurs lashes.
A brief treatment of the relevant laws can be found in the Shulchan Aruch, YD 64-65; various special “kuntresim” that were published over the years deal with the topic in greater detail. Rema, however, twice states (YD 64:7 and 65:8) that nikkur cannot be learned from a text, only through apprenticeship. This is due both to the fact that much of nikkur depends upon local custom and to the difficulty of learning the process without actually doing it. It is detailed work, requiring anatomic knowledge, surgical skill, patience and knowledge of tradition.
Until relatively recently the majority of Jewry performed nikkur on both the forequarters and hindquarters of the animal. Indeed, there is no indication in either the Shulchan Aruch (Rabbi Yosef Karo; 1488-1575) or Rema (1520-1572) that the discussions of nikkur are anything other than practical.
Rabbi Moshe Sternbuch (Teshuvot Vehanhagot 1, YD 418-419) claims that Maharshal (Rabbi Shlomo Luria, 1510-1574) established a custom that “Godfearing people refrain from eating hindquarters.” Rabbi Shlomo Machpud (Madrich Hakashrut of Badatz Yoreh Deah , 5:90) asserts that Rabbi Sternbuch’s claim is based upon a misreading of Maharshal. Rather, Rabbi Machpud states, the custom Maharshal established was to refrain from eating the hindquarters until a second menakker inspected what the first one did. Indeed, he writes that Maharshal ate the hindquarters of all animals save for those of small, delicate calves.
Examining Maharshal in the original supports Rabbi Machpud’s contention. In Yam Shel Shlomo (on Chullin 2b, no. 2, p. 2 andChullin 93b, no. 19, pp. 179-180 in the 5755 edition and cited in full in Be’er Hateiv YD 65:6), Maharshal records that in the “old days” in Germany nikkur was not so difficult. However, new stringencies made nikkur a far more arduous task, leading to grave mistakes. Overwhelmed by time-consuming stringencies, local menakkrim, who could not always keep up with the demand for hindquarters, would sometimes neglect to excise some of the forbidden sections. Thus, writes Maharshal, he therefore does not eat hindquarters until he has a second menakker check the work of the previous one, a practice he says was already instituted by Maharam Mintz. Evidently, Maharshal neither refrained from the consumption of hindquarters nor did he prohibit others from consuming them. He was simply ascertaining that the nikkur was done properly.
At some point the practice of not eating the hindquarters did indeed develop. This was due to several factors including the difficulty of porging, a lack of trust in the skills of the porgers and the easy sale of the hindquarters to non-Jews. One of the first to describe this practice, Sephardic Rabbi David ben Solomon ibn Zimra (Egypt/Israel, 1479-1573; Shu”t Radbaz 162) mentions a local custom of selling then hindquarters to Muslims. This practice is subsequently mentioned by Ashkenazic sources including Rabbi Menachem Mendel Krochmal (1600-1661; Tzemach Tzedek, no. 73), who makes note of the shochetim who went to the villages around Nikolsburg, sold the hindquarters to the non-Jews in the villages and brought only the forequarters to the Jewish community. Additionally, Rabbi Yair Chaim Bachrach (Germany, 1638-1702; Chavot Yair 178) discusses an individual who supported himself by selling the hindquarters of kosher meat to non-Jews.
In 1614, Rabbi Leon Modena (1571-1648), a well-known Venetian rabbi, was commissioned by an English lord to write a description of Jewish practices for King James I of England. His work, published in 1637 in Italian as Historia de gli riti Hebraici, was the first description of Jewish ritual written by a Jew in the vernacular explicitly for a non-Jewish audience. Rabbi Modena wrote:
Whence it is, that in many places in Italy and in Germany especially, they do not eat the hindquarters; because this sinew [gid hanasheh] is in them, and a great deal of fat, which requires much exactness to be taken away clean; and there are but few that can do it as it should be.
The kabbalist Rabbi Chaim Vital (1542-1620), the star student of Arizal, wrote that his teacher explicitly told him to partake of hindquarters as long as the nikkur was meticulous.
Indeed there were many towns in Europe where nikkur was practiced in recent centuries. Rabbi Yechezkel Landau (1713-1793; Noda B’Yehudah, Mahadura Tinyana, YD:31) notes that in Prague nikkur was practiced, but he acknowledges that there were cities in which there were no trained menakkrim and thus, for purely practical reasons, it was not practiced there.
Rabbi Yonatan Eibeschuetz (1690-1764) was a master menakker who was acutely aware of the difficulty of doing nikkur correctly; in his work Kreiti Uplati he writes that he only eats hindquarters if he himself is the menakker. The Yeshuot Yaakov (YD 64:2; Rabbi Yaakov Meshulam Ornstein, 1775-1839) testifies that in all the big cities, such as his community of Lvov, as well as in Brodt and Krakow, nikkur was performed. Rabbi Yechiel Michal Epstein (1829-1908; Aruch Hashulchan, YD 65:31) explains that in his town (Novardok, Russia) nikkur was under strict rabbinical control, performed not by the butchers but rather by specially trained and licensed menakkrim. As a further safeguard, the rabbis banned the importation of meat from outside the city.
While the Chatam Sofer (1762-1839) attests to the fact that in Pressburg (Slovakia) nikkur was not performed because of the effort involved, at the same time nikkur was practiced in Lissa and Prague.
Nikkur was performed in Melbourne, Australia, throughout the nineteenth century, although it is not clear when the practice ended.
In the early nineteenth century nikkur was still practiced in Hungary as evidenced by the publication in 1825 of Beit Yitzchak by Rabbi Yitzchak ben Eliezar. In his work, which was a practical guide to the halachot of nikkur, the author states that a menakker should not be overly strict and remove meat that need not be removed halachically, causing undue financial loss (siman 4; klal 3). Just as it is prohibited to permit that which is prohibited, it is likewise prohibited to prohibit that which by law is permitted.
A great detail of information is available about the practice of nikkur in London and Yerushalayim, places where it was practiced well into the twentieth century.
In London, nikkur was first introduced by the London Board for Shechita in 1827. It seems that housewives were not happy with the appearance of the porged meat. Butchers tried to satisfy their demands by selling unporged hindquarters. In 1865, the tension between the board, the butchers and the housewives reached such levels that a representative was sent to observe the methods of nikkur practiced in Leghorn, Italy, and in Paris in the hopes that nikkur was done there in a “neater” manner. Unfortunately, there were no differences in the methods. The conflict between the housewives, the butchers and the Board continued for decades. Eventually, the Board licensed only certain butchers to sell hindquarters. This led to other problems, and in 1912 and again in 1923 special campaigns were initiated to educate the public about the importance of nikkur and to enforce the regulations. Sometime after 1929, the beit din of the Board prohibited the sale of hindquarters, though some nikkur apparently continued in London until at least 1941. In 1941 Rabbi Yechezkiel Abramsky supported Rabbi Binyamin Beinish Atlas of Glasgow in rejecting the butchers’ request to sell hindquarters. His concern was that it could lead to problems of supervision (See Seridim 13 [Cheshvan 5753]: 3-4 for the exchange of letters). The issue arose again in 2000 when the Israeli chain El Gaucho sought to open a kosher branch in London and to serve hindquarters as it does in Yerushalayim. The beit din of the Board eventually turned the store down.
In Yerushalayim, nikkur of the hindquarters was actually instituted by the Ashkenazim. For many years Sephardim were the majority in Yerushalayim, since the modern community was established by Jews expelled during the Spanish Expulsion. Sephardim slaughtered only goats and sheep on which they practiced nikkur of the forequarters, but nikkur of the hindquarters was not done because of the animals’ small size. Following the arrival of the students of the Gra and of the Ba’al Shem Tov to Palestine in the early nineteenth century, the Ashkenazic community grew. However, the Turks prohibited the Ashkenazic community from performing its own shechitah. Finally, in 1874, when the Ashkenazic community was granted the right to slaughter, it continued to follow the custom of the Sephardim and only performed nikkur of the forequarters on goats and sheep. Moreover, the Ashkenazic community adopted the Sephardic customs as regards nikkur of the forequarters. This resulted in Yerushalayim Ashkenazim performing nikkur of the forequarters differently than other Ashkenazim.
In 1876 the Yerushalayim Ashkenazim initiated kosher slaughter of cattle; they now introduced nikkur achoraim in Yerushalayim, based on the practices of the Lithuanian Jews. The following year Rabbi Yehoshua Leib (Maharil) Diskin of Brisk, an expert in nikkur, moved to Yerushalayim, and together with Rabbi Shmuel Salant established a va’ad shechitah to ensure that the shechitah and nikkur were performed in the strictest manner.
Outside of Eretz Yisrael, the issue of nikkur was raised again during World War II. By the start of WWII, Jews in most parts of Poland no longer practiced nikkur. In March of 1938, the Polish Siem passed legislation forbidding the sale of kosher-slaughtered meat to non-Jews. Rabbi Chaim Ozer Grodzinsky wrote that in a rabbinic meeting held in Warsaw it was ruled that all Polish Jewish communities, without exception, should immediately reintroduce the practice of nikkur achoraim to avoid significant financial loss to the local Jewish population. There was no halachic problem in instituting nikkur, stated Rabbi Chaim Ozer. Even though nikkur was not practiced because of the lack of qualified menakkrim, avoiding the consumption of hindquarters was not an actual custom, he said.
In Israel, nikkur continued to be practiced. In 1943 Rabbi Nachum ben Avraham Kohen Levin wrote Torat Nikkur HaYerushalmi, in which he explained all aspects of practical nikkur of the forequarters and hindquarters. As described above, the Ashkenazim in Yerushalayim porged the forequarters of animals differently than did other Ashkenazim. Newcomers to the Land started to question the nikkur practiced in Yerushalayim, and Rabbi Levin hoped to show that it was in accordance with halachah, and that the differences that existed involved custom only. Clearly, nikkur was alive and well in Yerushalayim in 1943.
Today, nikkur of the hindquarters is practiced in Israel, and is supervised by many of the Sephardic badatzes as well as the Rabbanut. In addition, the OU supervises nikkur of deer hindquarters in the United States, because in deer, only the gid hanasheh and blood require removal, but not the chailev.
According to Rabbi Dr. Moshe Tendler, in both his father’s hometown of Kamenitz and Rabbi Moshe Feinstein’s hometown of Luban, Belarus (where Rav Moshe’s father-in-law was the shochet and menakker), nikkur was performed in the early twentieth century.  People did not stop practicing nikkur because of a ban or custom. Rav Moshe states this very clearly (Iggerot Moshe YD:2:42; pp. 56-57). In his opinion nikkur was not regularly practiced in recent years because butchers didn’t want to expend the effort, and there were enough non-Jews to purchase the meat.
Rav Moshe (Iggerot Moshe OC 5:28) states categorically that it is a grave sin to cause a section of the Torah to be forgotten even if it will not lead to the violation of any prohibitions.
Certainly to forget all of the laws of nikkur would fall under this sin. Doing so would also make it impossible to reinstitute the korban Pesach, which cannot be properly prepared without knowing how to remove the chailev and the gid hanasheh. 
1. To ensure that it is not a “treifah.” See Ari Z. Zivotofsky, “What’s the Truth about ... Glatt Kosher?,” Jewish Action (winter 1999): 75-76 for a discussion of treifah.
2. The blood in the organs is removed via salting or roasting. According to the letter of the law there is no need to remove any blood vessels; it is sufficient to sever them and salt the meat, and that is what the Sephardim and Yerushalayim Ashkenazim do. All other Ashkenazim follow the stringency of Rema in the Darkei Moshe and remove certain blood vessels. In a letter, which Rabbi Avraham Yitzchak HaKohen Kook (Da’at Kohen 223, cf., no. 46) sent to Rabbi Chaim Ozer Grodzinsky, he explained the lenient view of the Yerushalayim Ashkenazim, which had been accepted by Rabbi Shmuel Salant. Rabbi Kook writes that while he was not pleased with widespread use of the leniency, because it was an established custom at that point, it could not be changed.
3. None of this applies to fish, and only very few blood vessels from fowl are removed (and this is done only in some communities). The chailev of a chayah (non-domesticated animal such as a deer or an antelope) is permitted as opposed to that of a beheimah (domesticated animal), which is not.
4. The meat between twelve and thirteen is part of the hindquarters. See Shu”t Chatam Sofer, YD:68; Noda B’Yehudah, Mahadura Tinyana, YD:31; Mishneh Halachot 10, no. 85, pp. 90-92 and Teshuvot Vehanhagot 4, siman 183, p. 174.
5. There is chailev on some of the organ meat, such as the white fat on the bottom of the liver.
6. The only other dietary prohibition that is as serious is consuming chametz on Pesach. Because of the severity of the prohibition, the Agur (Rabbi Yaakov Landau, fifteenth century; #1175) counsels to rule stringently on all questions regarding prohibited fats.
7. Jeremiah Joseph Berman, Shehitah: A Study in the Cultural and Social Life of the Jewish People (New York, 1941), 25, claims, I think erroneously, that even in the Talmudic period there was a practice among some Jews to sell the hindquarters to non-Jews.
8. A book on nikkur published in Krakow in 1577 states that every word was reviewed by Rema and includes many questions asked by the author directly to Rema.
9. Note that this statement is found in the 5752 edition; it is absent in the 5746 edition.
10. The hindquarter section can be divided in two: the flanks, loins, waist and kidneys, from which fat must be removed, and the thigh, which has no fat but from which the sciatic nerve must be extricated (Torat Nikkur HaYerushalmi, p. 18).
11. Sec. 2, chap. 7, par. 3. I thank Professor Howard Adelman for help in locating this quote.
12. Sefer Hachezyonoat: Yomono Shel Rav Chaim Vital, ed. Moshe M. Faierstein, 4:2 (5766), p. 134; 4:8, p.138; Jewish Mystical Autobiographies, Book of Visions and Book of Secrets, trans. and introd. Morris M. Faierstein, (New Jersey, 1999), 156, 162; Sefer Torat Hagilgul, Sha’ar Shmini-Sha’ar Hagilgulim 1 (5757), 50. Cf., Sefer Yemoat Olam, ed. Chayim Meir Arnstar (Jerusalem, 5760), 94 and Meir Einei Hagolah, no. 297, p. 73).
13. See Shnayer Z. Leiman, Rabbi Jonathan Eibeschuetz and the Porger: A Study in Heresy, Haskalah, and Halakhah (New York, 2004) for a fascinating tale regarding Rabbi Eibeschuetz and nikkur. Hear a lecture featuring this tale at http://www.ou.org/audio/5764/mesorah64.htm.
14. Not all butchers in the city sold treibered hindquarters. The Aruch Hashulchan notes (YD 64:54) that in fact most places did not perform nikkur on the hindquarters and instead sold them to non-Jews. And in YD 65:7 he again notes that in his town there are those who did not perform nikkur.
15. Shu”t Chatam Sofer, YD:68.
16. Joseph Aron and Judy Arndt, The Enduring Remnant: The First 150 Years of the Melbourne Hebrew Congregation 1841-1991 (Melbourne, 1992), 321.
17. This is a paraphrase of Rebbi Eliezar’s statement in Yerushalmi Terumot, chap. 5. In a similar vein Rabbeinu Nissim, in his Viduy Hagadol before Yom Kippur, includes: “I have forbidden what You permit and permitted what You forbid,” indicating that the two are equally wrong.
18. The following description is from Albert M. Hyamson, The London Board for Shechita: 1804-1954 (London, 1954), 16, 32-33, 73. A slightly different history is presented by Rabbi Jeremy Conway, director of the London Beth Din Kashrut Division, “Why Rump is a Steak too Far,” The Jewish Chronicle, 23 June 2000.
19. It indeed looks “butchered,” and about 13 to 19 percent of the meat of the hindquarters is lost by porging. See Nachum Cohen Levin, Gevul Rishonim (5720/1960), 42-43, for a breakdown of what percentage of each section is removed.
20. See Dayan Grunfeld, The Jewish Dietary Laws 1 (1972), 67 and a letter by Alfred Magnus, president of the London Board for Shechita, in The Jewish Chronicle, 3 March 2000.
21. Details of the saga can be found in The Jewish Chronicle, 25 February, 3 March, 10 March, 9 June, 16 June, 23 June and 30 June 2000.
22. See Torat Hanikkur HaYerushalmi, (1943), 32-35.
23. See Shu”t Divrei David (35) that nikkur was practiced only on large animals. Yemenites and some Sephardim do perform nikkur achoraim on goats and sheep. Ironically, Torat Nikkur HaYerushalmi, 33, a strong advocate of nikkur, rails against those who do nikkur achoraim on sheep and goats and calls it a great “stumbling block” that should be stopped. In the time of Rema nikkur was still practiced on sheep as evidenced by a comment in Darkei Moshe (YD 64) and one in Maharatz, Seder Hilchot Nikkur (30a) as well.
24. These customs were instituted by Rabbi Chizkiya DiSilva, author of the Peri Chadash (d. 1698) when he was a rav in Yerushalayim.
25. Iggerot Rav Chaim Ozer 1 (Bnei Brak, 5760), no. 489, pp. 513-515, no. 490, pp. 515-516 and Shu”t Achiezer 3:84 (Iyar 5698 ).
26. In response to this initiative, Rabbi Ben Tzion Halberstam, the Bobover Rebbe, wrote a letter to Rabbi Chaim Ozer (reprinted in Tzohar [Tevet 5760], 7:397-398), where he conceded that although we can’t ban the practice of nikkur, “those who are extra careful should avoid the hindquarters.”
27. He notes that nikkur of the chailev around the four sections of the animal’s stomach was not performed commercially in Yerushalayim because of the effort involved, rather Sephardic women did the nikkur themselves. It seems that it was an old custom for women to do nikkur—the Beit Yosef (YD 64) records a tradition regarding nikkur that he heard from “nashim kesheirot from Spanish lineage.” There are also many comments in Maharatz’s Seder Hilchot Nikkur regarding his asking women about the practice.
28. Rabbi Dr. Moshe Tendler reports (telephone conversation with the author, 26 July 2005) that Rav Moshe would often comment when eating meat at the Tendler household on yom tov that it just wasn’t the same as the tasty hindquarter meat they had in the old country.
29. I thank Rabbi Daniel Eidensohn for pointing out this source to me.
30. See Rambam, Hilchot Korban Pesach, 10:11 and Ra’avad and Kesef Mishnah there.
Reprinted from JEWISH ACTION Magazine, Fall 5767/2006 issue