The State of Israel & rebelling against the nations
A: 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 or the Shulchan Aruch. 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 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 Halachah, we must follow one of them. The Ramban is well-known to all and there are many of his rulings 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.
Ha-Rav Meir Simchah – the Or Sameach – wrote in a letter of support for "Keren Ha-Yesod" ("The Foundation Fund" established to raise money and invest in the Jewish Homeland) that even according to one who claims that there is a prohibition to rebel against the nations of the world, we did not rebel or take the Land by force since the British gave us the Land. And after the British gave us the Land, the Arabs attacked us. We did not rebel against them, they came and attacked us. By permission of the nations of the world in the Balfour Declaration, San Remo and the UN vote, the prohibition fell even according to those who claim that such a prohibition existed.