Many times the Rebbe invited the Rabbis and Torah giants who were present at farbrengens to make known their Halachic opinions regarding the prohibition of giving away land. For example, on 10th Shvat, 5736 (1976), the Rebbe said:

When seventy-two Rabbis will make a resolution that the scheme of the nations should be for naught — because the Jews have an everlasting covenant on the entire Land of Israel, together with the whole Torah of Israel and the nation of Israel — then our actions will outweigh the attempts by the nations of the world to pry the Land of Israel from us. All of their worthless schemes will be totally quashed, so that even those who are enthusiasts of such ideas will see that their views are not consonant with reality.

In practice, what must be done now? A Rabbi must be designated to stand up and expound, according to Torah, the sole Jewish claim to the Land of Israel. Afterwards, all the other seventy-one Rabbis will concur, and the whole world will answer, “Amen, Amen.”

After the Rebbe finished saying these words, those present held a unique vote, and more than one hundred Rabbis raised their hands in agreement.1

Similarly, on the night of Shmini Atzeres, 5742 (1981), before the fifth hakkafah, the Rebbe said:

Since we are all in the midst of a particularly auspicious time — being that it is Yom Tov, and especially since we are in the midst of the hakkafos of Shmini Atzeres — this is an appropriate time to totally neutralize all opposition to the concept of shleimus haAretz, in a manner which will also nullify all undesirable incidents which have taken place in the past in connection with this matter.

Therefore, it would be appropriate that during this hakkafah (Melech Olamim2 ), that all the Rabbis who are present and who are authorized to rule in matters of Jewish law, whom our Sages call “kings [rulers],”3 issue a clear, obligating ruling which reiterates that the entire Land of Israel belongs to the nation of Israel.

And their ruling will not be expressed in a pompous manner [kochi v’otzem yodi], but rather with the authority of the Holy One. This is because the authority of these Rabbis derived from a continuous chain of authority dating all the way back to Moshe Rabbeinu, who was given the authority by G‑d, Melech Olamim. As a result, when these Rabbis issue such a ruling, especially at such an auspicious time, then the ruling of the rulers — the Rabbis — will flow from the Melech Olamim, such that it will automatically have a stark and recognizable effect on all the worlds, even on the physical level, and even on the nations of the world.

The Rebbe then continued:

Concerning the actions which must be taken: During this hakafah (Melech Olamim), the rulers — the Rabbis — who deal with practical Halachic rulings (for this is their job) should issue a clear ruling that the entire Land of Israel belongs to the nation of Israel.

Here we see the great importance that the Rebbe attaches to the concept of a pointed ruling on this subject. But on another occasion the Rebbe referred to a certain ruling which was issued a generation ago. This is none other than the resolution of the “Great Assembly”4 (5697-1937) which resolved that each and every compromise made regarding the Holy Land, which was given to us by the Holy One according to its boundaries,5 is null and void.

These are the Rebbe’s comments, on Motzoei Shabbos Mishpatim 5738 (1978):

The explicit ruling which was issued at the Great Assembly states that it is unequivocably forbidden to surrender even the tiniest particle of land within the boundaries of the Holy Land. It is astonishing that people do not publicize and proclaim this ruling in the greatest possible way. The fact that there are those who wish to conceal the ramifications of this ruling by concocting contrived interpretations of it, will be to no avail. This ruling is like every other Jewish law, for “the word of G‑d will certainly endure.”

The Rebbe concludes:

May it be G‑d’s Will that everyone will look at the Code of Jewish Law, chapter 329 (if they do not want to trust me), and they will see that the law is clear: it is forbidden to cede even a small piece of the Land of Israel to a non-Jew. The students and descendants of those Torah giants who participated in the Great Assembly in Marienbad should publicly proclaim to their students that they have a clear ruling instructing us how to conduct ourselves. They should continue spreading word of this until all the Jews know of the ruling.”

The Rebbe even referred to those situations where there is nothing that can be done except protest:

Since we see that we have to contend with these people — it is a sign that our only concern must be to protest against their actions which are not in accordance with the Torah. They are in conflict with the Torah, and the ruling of the Code of Jewish Law, Laws of the Sabbath.6 This law states that one must take up arms on the Sabbath and not allow the enemy to approach a border town. This law even applies outside of Israel, because the issue at hand has nothing to do with who the land belongs to, or the concept of not antagonizing the nations; the one and only reason for this ruling is the danger to the lives of large numbers of Jews, G‑d forbid.

Regarding the effectiveness of a Rabbi’s ruling, we may take note of the Rebbe’s address of Sivan 28, 5746 (1986):

Every Rabbi in his respective generation is a leader in that generation — like a giant among knights; as the Prophet Shmuel was in his generation, or Moshe in his. When such a Rabbi issues a ruling of Jewish Law, it has an effect on the world — on the world, in such a way that the reality of the world shall conform to the ruling the Torah.7