Editor's Note: Here is an interesting short sketch of how the chameleon-like rabbinic law (halacha), which is often situation ethics, except when a core principle is at stake (such as the alleged ethnic and ethical supremacy of "Klal Israel" i.e the "Jewish" nation over the depraved goyim) ---is decided based on the demands of the zeitgeist. For hundreds of years it was a heresy in Judaism to seek to found the Israeli nation-state by armed intervention before the coming of the Moshiach (Messiah). With the success of Zionism however, other halachos were conveniently excavated which justified what had once been forbidden. This is the same spirit that informs the US Supreme Court's situation ethics approach to the US Constitution. This is why Associate Justice Antonin Scalia, the alleged "conservative," is such a keen student of rabbinic halacha.
Glossary note: "Gemara" = Babylonian Talmud
Question: How was it possible to establish the "State of Israel" when the Gemara (Ketubot 111a) says that it is forbidden to rebel against the nations of the world?
Answer: While the Gemara in Ketubot does mention the prohibition of rebelling against the nations of the world, it is not found in the law codes – not in the Rambam (Rabbi Moses Maimonides) or the Shulchan Aruch (of Rabbi Joseph Karo).
There are two possibilities why this is so:
1. It is a dispute and we did not hold this way (Our Rabbi, Ha-Rav Tzvi Yehudah, Le-Netivot Yisrael, vol. 2, p. 217).
2. This is not a legal (halachic) issue but a homilectic (aggadic issue) (see Shut Avnei Nezer, Yoreh Deah #454 and Ha-Rav Menachem Kasher's "Ha-Tekufah Ha-Gedolah," p. 187).
There is a commentary to the Rambam's Sefer Ha-Mitzvot called "Megillat Ester" by Ha-Rav Yitzchak Leon and he did in fact write that it is forbidden to conquer Eretz Yisrael since it is it is forbidden to rebel against the nations of the world.
He (Ha-Rav Yitzchak Leon ) argued with the Ramban who said that it is a mitzvah to conquer the Land of Israel throughout all generations (Additions to the Sefer Ha-Mitzvot, positive mitzvah #4).
It is thus a dispute between the Ramban and the author of "Megillat Ester." According to the general rules of deciding Halacha, we must follow one of them. The Ramban is well-known to all and there are many of his rulings (included) in the Shulchan Aruch, while there is not even one law from the "Megillat Esther."
Furthermore, the Rambam did not cite the Gemara that it is forbidden to rebel against the nations of the world.