The Chazon Ish, who is quoted on your website today in an anti-zionist context, also wrote the following to R. Betzalel Zolti, Chief Rabbi of Jerusalem (Kovetz Torah Sheb'al Peh, 11, page 44): "I can find no pretext to allow selling land either to a non-Jew or to a Jew suspected of selling to non-Jews."
We are not talking here about sovereign land, but of personal property. However, what is the idea behind this rather strong halachic ruling?
The Rambam explains, hil. Avodah Zorah 10:3:
We do not sell them houses and fields in Eretz Yisrael...neither do we lease fields to them...Why were our sages strict regarding fields? It is because leasing them to non-Jews has two negative results: it diminishes the tithes and gives non-Jews a foolthold on the land. WE ARE ALLOWED TO SELL THEM HOUSES AND FIELDS OUTSIDE THE LAND BECAUSE IT IS NOT OUR LAND.
That is the basis for the Chazon Ish's ruling. And look how far he goes with this! We are not even permitted to sell land to a Jew who is merely suspected of selling land to a non-Jew!
This is the same Chazon Ish whom you quoted in an anti-zionist context. Of course, the Chazon Ish may have well been opposed to and Israeli government as it is. Yet, at the same time he is clearly and strongly opposed to non-Jews gaining a foothold in our land. I suppose that means he was not in favor of the idea of non-Jews being given control over the entire land.
You quote the Rambam who gives a reason of "not allowing them a foothold" to show that the same should apply to sovereignty. But the Chazon Ish wrote clearly that the Rambam's reason plays no role in determining halacha; we do not "darshan taama dikra." The proponents of the temporary sale of land to a non-Jew in order to exempt it from Shmittah restrictions (heter mechirah) argue that it is unusual for the Rambam in the Mishneh Torah to offer the reason for a mitzvah. The Rambam presents the reason for this prohibition, they argue, because the prohibition applies only when the reason applies. Thus, since the sale for Shmittah is only temporary in nature and the non-Jew is not given the opportunity to reside permanently in Eretz Yisroel, the prohibition does not apply. But the Chazon Ish (Shviis 24:4) flatly rejects these arguments and writes, "The Torah was not given with these distinctions; any time one sells to a gentile he transgresses this prohibition, even if it seems to us that he is not taking up residence in it."
Thus according to the Chazon Ish, the reason given by the Rambam plays no role in determining halacha. One is forbidden to sell land even if it does not lead to non-Jews settling permanently, and by the same token one is permitted to give away political sovereignty even if it does lead to non-Jews settling permanently. And even according to the proponents of heter mechirah, who understand the Rambam as taama dikra (a reason that modifies a law), we know that taama dikra can only work to limit the application of a prohibition; it cannot create a new prohibition. For example, Rabbi Shimon holds that when the Torah forbids taking the garment of a widow as collateral, it means only a poor widow (Bava Metzia 115a). But he does not use his reasoning to extend the prohibition to all poor people. Here too, limiting the prohibition to permanent sales and thus permitting the sale of land for Shmittah is one thing, but claiming that the prohibition applies to something that is not a sale at all is quite another thing.
Once non-Jews have political control, they will certainly not allow lo sechanem on private property to be kept. Sellers of land would be prohibited from discriminating on the basis of race or religion. If the new regime is non-democratic, they may simply force a large number of Jews to leave their land. At that point, taking compensation for the land would be permitted since in any case the outcome is the land will be occupied by non-Jews. Furthermore, even if the new regime is democratic and fair-handed, they may force Jews to give up ownership of land that was acquired illegitimately, i.e. by expelling or intimidation of the Palestinians in 1947-8 or 1967.
In the time of Nevuchadnetzar when the Jews went into exile, some of them retained ownership of their land so that when they returned from exile they went back to it. Yirmiyahu Hanavi said, "They will buy fields with money, write documents and sign, and place it in an earthenware vessel so that it lasts a long time." Yet for all intents and purposes, Babylonia had conquered the land and so they used it (or could have used it) during the 70 years of exile. This could be a model for our situation today. Jews will retain ownership of their individual plots of land but perhaps be forced to leave them by the new government. They will retain their documents so that when moshiach comes they can prove that the land is theirs.