(was originally written by R' Yaakov Shapiro)
Besides the slew of poskim and Gedolim from all walks of Torah Judaism who quote the Oaths l'halachah, pick up the Zionist journal "techumin" Vol. 10, and you will see the Oaths quoted l'halachah by none other than Rabbi Ovadiah Yosef.
He discusses the issue of "Land for Peace", and mentions the fact that Hisgarus B'Umos - antagonizing the nations of the world - is against the Torah, prohibited by virtue of the Oaths.
He says that if the nations of the world demand Israel give back land in return for peace (of course it has to be a real deal), and doing so would prevent war, then we are obligated to do so, and we are not allowed to go to war in order to maintain the land. We would be obligated to give the land back because of Pikuach Nefesh.
He quotes the Megilas Esther that says the reason the Rambam omitted the Mitzvah to live in EY nowadays is because the Oaths negate the Mitzvah. (note Rambam says at the end of Iggeres Teiman: “And these are things the prophets have already foretold, and they have told us about what I have told you, that when the time of the true moshiach draws near, there will be many who lift themselves high and place doubts in people's minds, but their claims will not be born out, and they will perish and many will perish with them. And when Shlomo, peace be upon him, made known with his holy inspiration, that this nation when it is sunk into exile will try to arouse itself not at its proper time, and they will die because of this and travails will come upon them – he warned against this, and made an oath against this in an allegorical way, and said (Shir Hashirim 2:7), ‘I adjure you, daughters of Jerusalem…’ And you, our brethren, our beloved – keep his oath and do not arouse the love before it is desired!”)
Then he quotes the Rashbash who says that the Ramban held that the Oaths only prohibit a massive national ascent to EY, but individuals who want to live in EY are not affected by the Oaths. The Rashbash points out that the Bnei Efraim were annihilated in the desert because they violated the Oaths, and warns us to take heed from what happened to them ("tzai ur'ah mah irah lbnei efraim.")
Then he quotes the Rivash who also brings the Oaths l'halachah.
Then he quotes other Achronim who apply the Oaths l'halachah, as well as those who hold l'halachah that the Oaths even negate the Mitzvah of living in EY for individuals - as per the Megilas Esther. They include Rav Yosef Dov Halevi Soloveitchik ZTL (the "Bais Halevi").
His conclusion l'halachah is that because of the Oaths, even the Ramban agrees that there is no Mitzvah at all nowadays to endanger Jewish lives to conquer Eretz Yisroel, and therefore, when you can obtain peace by giving up land, you are obligated to give up land because of Pikuach Nefesh.
(Interestingly, later on he refutes one of the most common Zionist blunders against the Oaths - that they expire after 1,000 years.
This is based on a misunderstanding of a statement in the Zohar, and other Kabbalistic works. Chacham Ovadiah says that first of all, it’s crystal clear in the Gemora, the Targum, the Rambam, and Rishonim and Achronim who all quote the Oaths l'halachah after the alleged expiration date, that the Oaths are in fact in effect until Moshiach comes. As for the Zohar, Arizal and Kabbalistic works, he refers the readers to the Satmar Rebbe's Vayoel Moshe, p. 85 and onward, where he says the issue has already been dealt with at length.
The Satmar Rebbe in fact shows that a proper understanding of the Zohar and the Kabbalah shows that they agree 100% with the Halachah, and that the idea that they said the Oaths expire is a total mistake.)