Much of the criticism directed at Israel and specifically the status of its post-1967 administration of Judea and Samaria (and until 2005, Gaza), revolves around the question of what is legal and what may be illegal/
One claim is that a partition of the Mandate area was recommended in November 1947 but was rejected by the Arabs, as the rejected the 1937 partition and other offers. Given that rejection, Israel surely has a claim to additional territory especially as the Arabs not only rejected but launched a war of aggression at that time to prevent Israel from being establishment. And since they continued their Mandate-era terror campaign throughout the 1950s and 1960s and then initiated a war in 1967 by closing the Tiran Straits, expelling UNO observers and by shelling Jerusalem and other locations in Israel, to which Israel responded defensively, causing Israel to react defensively, the areas gained legally belong to Israel twice-over: being part of the original Mandate area within which a Jewish national home was to be reconstituted and due to the nature of the 1967 war.
At this point, I wish to introduce one other aspect: the 1939 British White Paper.
That policy change, and here I follow the letter of the United Kingdom Delegation to the United Nations of August 18, 1947, intended to put an end to uncertainty as to the objectives of England's policy in Palestine, and to prepare the way for the termination of the Mandate. In opposition to the interpretation of the Balfour Declaration contained in the White Paper of 1922, the British government “now declare unequivocally that it is not part of their policy that Palestine should become a Jewish State.”
However, at the same time, it "maintained the rejection of the Arab contention that they were pledged, by undertakings given during the war of 1914-18, to grant independence to the Arab population of Palestine as it could not agree that the McMahon correspondence forms a just basis for the claim that Palestine should be converted into an Arab State.”
There was to be a ten-year period of transition at the end of which the new independent State should enter into treaty relations with the United Kingdom.
As for Jewish immigration, not more than 75,000 additional immigrants during the five years beginning in April, 1939 would be permitted, and furthermore, “no further Jewish immigration will be permitted unless the Arabs of Palestine are prepared to acquiesce in it.”
The last section of the White Paper dealt with the transfer of land form Arab to Jewish ownership. Up until 1939, the Administration of Palestine is required, under Article 6 of the Mandate, to encourage “close settlement by Jews on the Land”, and no restriction had been imposed, the Paper claimed, on the transfer of land from Arabs to Jews. But the White Paper gave general powers to the High commissioner to prohibit and regulate transfers of land.
The policy expounded in the White Paper was bitterly condemned by all Zionist opinion. The Zionist Congress of 1939 denied its moral and legal validity, and declared that the Jewish people would not acquiesce in the reduction of its status in Palestine to that of a minority. The Arabs criticised the length of the period of transition, the provision for its possible prolongation, and the proposal that representatives of the mandatory Power should participate in framing the constitution of the independent State.
That was the background.
Paragraph 110 of that letter than noted:
The Mandatory’s new statement of policy was examined by the Permanent Mandates Commission at their thirty-sixth session in June, 1939. the commission reported that:
“the policy set out in the White Paper was not in accordance with the interpretation which, in agreement with the Mandatory Power and the Council, the Commission had always placed upon the Palestine Mandate.”They went on to consider whether the Mandate was open to a new interpretation with which the White Paper would not be at variance. Four of the seven members
“did not feel able to state that the policy of the White Paper was in conformity with the Mandate, any contrary conclusion appearing to them to be ruled out by the very terms of the Mandate and by the fundamental intentions of its authors.”The other three members “were unable to share this opinion; they consider that existing circumstances would justify the policy of the White Paper, provided the Council did not oppose it.”
In other words, the White Paper with all its restrictions and fundamental alteration of policy was, yes, illegal.
And unfortunately, the League of Nations Council was prevented from either approving or invalidating that White Paper due to the outbreak of war in September.
The 1947 Partition was rejected and became a dead letter.
The 1939 White Paper was illegal.
The 1937 Peel Partition was never accepted by the Arabs.
There is nothing illegal about Jews residing in Judea and Samaria, where they have always lived, except for the 19 years of Jordan's illegal occupation and annexation of the area when Jews were banned, as well as the 30 years of the Mandate period when Arabs engaged in a successful ethnic cleansing campaign forcing Jews out of Gaza, Samaria, Judea and the Jerusalem area.