Many pamphlets were written about legalizing marriage with one's sister-in-law (link), including one essay by the Rev. T. Berney, called "Marriage With a Deceased Wife's Sister or with a Niece, Contrary to the Holy Law of God, and to the Laws and Customs of the Jews, and to the Teaching of Our Lord Jesus Christ and of His Apostles, and to Nature" (link). He sent this epistle to Parliament, and it was printed in 1885.
He begins informing Parliament that they have been led in error by those who claim that such marriages are biblically permissible. He will show that this is not so. He reminds them that Britain faces trials and judgments by God, such as recent military disasters in Sudan, which were due to God's removal of his blessings on Britain because of its "present unrighteous law of divorce." He aims to show them that passing a law permitting the marriages described would defile the land and bring curses upon it, in accordance with Deut. 11:26 - 28. What then follows is a discourse on Lev. 18:18, which deals with sexual relations with a wife's sister. He gives an interesting Hebrew lesson, pointing out what precisely certain words mean, in contrast to the way they are translated in the Authorised (King James) Version.
After proving to his satisfaction that such a marriage is firmly prohibited, he moves on to the next area mentioned by the title of his essay, namely the Jewish view. So he turns to "the Oral traditionary of the Jewish people, now commonly called the Mishna" with regards to "Yeboom" (Yibum; Levirate marriage). Before he gets to it he remarks in passing that the Reform Jews permit such a marriage, but they are irrelevant, because "the denomination of Jews called " The Reformed Jews " are a mere set of Dissenters from the Orthodox Jews: and I am informed on reliable Jewish authority, that they sprang up into notice only at the beginning of this century." He explains that "Dr. Marks is the Chief Rabbi in England of this Jewish sect," and Parliament should be aware that letters and opinions quoting him and !! Dr. N. Adler !! "and other learned Hebrew Professors who are members of these Sects" have no value whatsoever.
Satisfied that he will only be showing the opinion of Orthodox traditional Judaism, he returns to the Mishnah. He refers to the 18 Treatises, the English translation of a part of the Mishnah by Rabbis David A. de Sola and M. J. Raphall (1845). He does not mention this, but interestingly enough, this early Mishnah translation appears to have been undertaken in part to combat the initiation of Reform in England. He proceeds to quote their introduction to Yevamos and no less than the translation of no less than 17 mishnayos which he claims support his contention. He then argues that if there is anything in the Mishnah which disagrees then clearly it is spurious later "tradition," rather than the genuine tradition which existed from Antiquity and which was known during the time of Jesus.
The reason he mentions this is because another pamphlet had quoted a Mishnah which did not support him (Yevamos 4.14). It rather unambiguously says, אשתו שמתה מותר באחותה, "If a wife dies, it is permitted to marry her sister." He claims, first of all, that the author wrote the pamphlet for money. Not only that, the Mishnah is spurious, and he infers this from the "fact" that de Sola and Raphall agreed with him, because they did not include this Mishnah in their translation! As it happens, they were prudish and omitted sensitive material from their translation, probably out of the sense that presenting it publicly dishonors Judaism.
He then claims that this particular Mishnah was only introduced after the year 1509 (!). The proof? R. Ovadyah Bertinoro does not comment on this Mishnah (and his commentary was written in that year, says he). There is yet another proof. The proof is that R. Moshe Isserles, the Rema, "in his remarkable edition of the Shulchan Aruch" calls them "Emendations" !!!
If you are feeling like you are falling down a rabbit hole reading these words, and everything is getting curiouser and curiouser, he continues to explain what he means. Citing Wolff (Bibliotheca Hebraea) he explains the history of the Shulchan Aruch. He then quotes the title page of the 1775 Latin edition of the Shulchan Aruch (Choshen Mishpat), " . . . R. Mosen Iserles emendato atque suppleto." In other words, the Shulchan Aruch features "Emendations" by Isserles.
He quotes one such Emendation, to the effect that " . . . even should he have children, and betroth himself to his deceased wife's sister, he may marry her immediately after the seven day's mourning; for she will have more care for the children of her sister than another will have." But "This passage is not to be found in the first edition."
In other words, the fact that the Rema added hagahot to the Shulchan Aruch is marshaled as evidence that the content therein is spurious and not the real halacha.
This is not enough for him. He continues to accuse the Chief Rabbi Nathan Marcus Adler of "audaciously and deceptively" quoting this "Emendation" in his letter to the Royal Commission, "as if it had formed a part of the original Shulchan Aruch." Can you imagine such a thing? How devious of Dr. Adler, quoting the Rema as if it were a real halacha.
Since the Rema's edition is from 1580 [sic; actually it's from 1578], it "enables us to arrive at an approximation to the dates at which the corruptions were made." It must be later than 1509 and earlier than 1578, when the Rema wrote his notes to the Shulchan Aruch (here he got the date correctly). He does not blame the Rema, it seems, as he keeps referring to it as a "remarkable edition."
This is not enough for him though, and he claims "that the perpetuation of these gross corruptions, in the books in the hands of some of the European sects of the Jews, resulted from the apostasizing example set by Pope Alexander VI (the infamous Borgia) in granting those Dispensations to the two Kings, Emanuel of Portugal and Ferdinand II of Sicily; the one to marry his deceased wife's sister, and the other his aunt." He explains that when the Jews were expelled from Spain, they were forced to flee to Portugal. The daughter of Ferdinand and Isabella was to be betrothed to the son of Emanuel of Portugal. But as a condition of this marriage, the sovereigns of Spain demanded that Emanuel expel the Jews from Portugal. This did eventually happen, but not right away. In the meantime, the princess died, and Emanuel wished to marry her sister. This is what he received a dispensation for from the Pope. And although "direct evidence . . . [has] not yet been obtained" he feels that he can suggest that as a concession to King Emanuel the Jews consented to let the Mishnah be corrupted! However, thankfully there are still Orthodox Jews [i.e., the first edition of the Shulchan Aruch] and Karaites who never corrupted their laws, and they strictly forbid a man from marrying his wife's sister after her decease!
Without a doubt this is one of the most amazing things I have ever read.
Edit: As someone mentioned in the comments, I really didn't clarify enough. It is totally baseless to suggest that any form of Rabbinic Judaism ever prohibited marriage with a sister-in-law, after a wife's decease, as is the suggestion that the Mishnah here has been tampered with, and after 1509 no less. Here is the Mishnah in the 1492 Naples edition: