Palestine legally existed in 1920 by the Allies and Axis powers signing the Treaty of San Remo and Treaty of Sevres.
You're lying.
There were not to be any Jewish involvement in the government of Palestine.
What government of Palestine?
You are obviously confused.
The only way to learn the truth is by reading what the British had to say about the British Mandate for Palestine.
So the Churchill Whitepaper of 1922 is a quick synopsis.
{...
Unauthorized statements have been made to the effect that the purpose in view is to create a wholly Jewish Palestine. Phrases have been used such as that Palestine is to become "as Jewish as England is English." His Majesty's Government regard any such expectation as impracticable and have no such aim in view. Nor have they at any time contemplated, as appears to be feared by the Arab deegation, the disappearance or the subordination of the Arabic population, language, or culture in Palestine. They would draw attention to the fact that the terms of the Declaration referred to do not contemplate that Palestine as a whole should be converted into a Jewish National Home, but that such a Home should be founded `in Palestine.' In this connection it has been observed with satisfaction that at a meeting of the Zionist Congress, the supreme governing body of the Zionist Organization, held at Carlsbad in September, 1921, a resolution was passed expressing as the official statement of Zionist aims "the determination of the Jewish people to live with the Arab people on terms of unity and mutual respect, and together with them to make the common home into a flourishing community, the upbuilding of which may assure to each of its peoples an undisturbed national development."
It is also necessary to point out that the Zionist Commission in Palestine, now termed the Palestine Zionist Executive, has not desired to possess, and does not possess, any share in the general administration of the country. Nor does the special position assigned to the Zionist Organization in Article IV of the Draft Mandate for Palestine imply any such functions. That special position relates to the measures to be taken in Palestine affecting the Jewish population, and contemplates that the organization may assist in the general development of the country, but does not entitle it to share in any degree in its government.
Further, it is contemplated that the status of all citizens of Palestine in the eyes of the law shall be Palestinian, and it has never been intended that they, or any section of them, should possess any other juridical status. So far as the Jewish population of Palestine are concerned it appears that some among them are apprehensive that His Majesty's Government may depart from the policy embodied in the
Declaration of 1917. It is necessary, therefore, once more to affirm that these fears are unfounded, and that that Declaration, re affirmed by the Conference of the Principle Allied Powers at San Remo and again in the Treaty of Sevres, is not susceptible of change.
...}
That clearly proves Palestine was to be Moslem Arab, independent rule.
Jews were only to be allowed facilitated immigration to a Jewish homeland WITHIN this independent Moslem, Arab, Palestine.
The Zionist Organization has pledged to never want any participation in rule, in the 1921 Carlsbad conference.