Q. Is there any halachic impediment in giving parts of Eretz Yisra’el to the Palestinian Authority?
A. The Torah says (Deut. 7:2), lo t’chonnem, literally “do not be gracious to them”. The Talmud (Avodah Zarah 20a) links t’chonnem with chanah, “to encamp”, understanding the verse as saying that once the land has come into Jewish possession it must not be alienated; territory promised by God must remain Jewish. There is therefore a religious obligation not to transfer any of the land.
Rav Soloveitchik said, however, that this obligation is – like other mitzvot (except for three, the duty not to murder, commit adultery or worship idols) – subject to the duty of saving life, pikkuach nefesh, and if real peace can be achieved by ceding territory, that would be pikkuach nefesh.