Balfour resigned as foreign secretary following the Paris Conference in 1919, but continued in the Cabinet as lord president of the council.
In a memorandum addressed to new Foreign Secretary Lord Curzon, he stated that the Balfour Declaration contradicted the letters of the covenant (referring to the League Covenant) the Anglo-French Declaration, and the instructions to the King-Crane Commission.
All of the other engagements contained pledges that the Arab or Muslim populations could establish national governments of their own choosing according to the principle of self-determination. Balfour explained: “… in Palestine we do not propose to even go through the form of consulting the wishes of the present (majority) inhabitants of the country though the American [King-Crane] Commission is going through the form of asking what they are.
Balfour stated explicitly to Curzon:
"The Four Great Powers [Britain, France, Italy and the United States] are committed to Zionism. And Zionism, be it right or wrong, good or bad, is rooted in age-long traditions, in present needs, and future hopes, of far profounder import than the desires and prejudices of the 700,000 Arabs who now inhabit that ancient land. In my opinion that is right." * * * * *
"I do not think that Zionism will hurt the Arabs, but they will never say they want it. Whatever be the future of Palestine it is not now an ‘independent nation’, nor is it yet on the way to become one. Whatever deference should be paid to the views of those living there, the Powers in their selection of a mandatory do not propose, as I understand the matter, to consult them.". . ."If Zionism is to influence the Jewish problem throughout the world, Palestine must be made available for the largest number of Jewish immigrants"
While the rights granted under the Trust restricted the Jews, when they did exercise sovereignty, from doing anything that would impair the civil or religious rights of the Arabs it was silent as to the political rights for the Arabs. The Mandate Law also became the domestic law of the UK and the US in 1924 as Treaty Law when, under a new American Administration, the Mandate became the subject of the Anglo American Convention of 1924.
Perfidious Albion did not maintain the 1920 form of its proposed trust for very long. Circumstances changed, British interests changed, and the British Government also changed. President Wilson's opposition had delayed the issuance of the mandate as proposed in the initial draft submitted to the WWI Allies at San Remo. In the meantime, England had installed Feisal as the King of Syria. After the Battle of Maysalun, in which the French Armed Forces defeated the Syrian Army the French deposed Feisal. Abdullah, Feisal's brother, was furious. He marched his troops from their home in the Hejaz (in the Arabian Peninsula) to Eastern Palestine and made ready to attack the French in Syria.
Churchill did not want war between the Arabs and the French. In the secret Sykes-Picot Agreement, Syria was in the French sphere of influence. Churchill gave Feisal the Kingdom of Iraq as a consolation prize and gave Abdullah and his Hashemite tribe from the Arabian Peninsula Eastern Palestine in violation of the British Mandate. The Mandate at San Remo had prohibited the Mandatory from ceding any land to a foreign nation. In the 1922 change, with a new Article 25, it formally approved delaying organized settlement by the Jews East of the Jordan River and informally gave TransJordan to Abdullah and his Hashemite Tribe from the Hejaz.
Article 25 preserved the prohibition of the Mandatory Power from discriminating among races or religions. The land East of the Jordan River became TransJordan and then Jordan and the Mandatory, despite the specific terms of the mandate, prohibited Jews, but not other ethnic groups, from settling there.
The British urging the League to adopt Article 25 was a breach of its fiduciary relationship as trustee with its beneficiary and as guardian, with its ward. as were the policies in their White Papers of 1922, 1930 and the vicious White Paper of 1939 under the Prime Minister Neville Chamberlain, of Munich fame, that blocked many Jews from fleeing from the Nazi Holocaust. A vicious enforcement of the blockade ensued and directly disobeyed the Mandate's requirement to facilitate Jewish immigration.
During WWI the Hussein/McMahon correspondence with the Arabs in the Arabian Peninsula led to a British offer to all Arabs in the Caliphate of self-government free from Turkish rule if they helped the British in the war.
The Arabs local to Palestine, unlike the Arabs from the Arabian Peninsula that had been led by Lawrence declined the British offer of political self determination if they were to help the Allies, and preferred to fight for the Ottoman Turks who ruled from Constantinople. According to Winston Churchill, , "The Palestinian Arabs, of course, were for the most part fighting against us, ,,," 
"However the Jews assembled several battalions of Jewish soldiers that fought alongside the British in Palestine in WWI.
At that point the Jews had, de facto, lost 78% of their Mandated beneficial right to sovereignty in Palestine, the land TransJordan or East of the Jordan River. Only 22% of the Mandate was left. After WWII, Article 80 of the UN Charter expressly preserved the rights that had been granted by the League of Nations prior to its demise, i.e. the Jewish national rights, so the UN could not grant any of it to the Arabs. As I have noted, the Mandate itself prohibited the trustee from ceding any land in Palestine to a foreign Power.
Known as “the Palestine clause,” Article 80 was drafted by Jewish legal representatives including the liberal Rabbi Stephen S. Wise, Peter Bergson (Hillel Kook) from the right-wing Irgun, and prominent Revisionist Ben-Zion Netanyahu (father of Bibi). It preserved the right of the Jewish people to “close settlement” throughout their remaining portion of Palestine west of the Jordan River.
In 1947 nevertheless, the UN did not “grant” but its General Assembly “recommended” (not a grant-- that would be inconsistent with the previous grant) a partition that offered a part of the area West of the Jordan (a part of the 22% remaining) to the Jews, in effect, releasing that part of the trust res (the political rights) to the Jews, and the remainder to the local Arabs, although the latter was unauthorized by the Mandate. In the UNSCOP hearings, the Arabs had threatened violence if the Jews were to have a state in any part of the Middle East. It is evident that the UN, by submitting to the Arabs extortion -- threats of violence -- and recommending still further partition of the remainder, hoped to avoid the violence.
In the San Remo Resolution, the Allies agreed
"To accept the terms of the Mandates Article as given below with reference to Palestine, on the understanding that there was inserted a process-verbal an undertaking by the Mandatory Power that this would not involve the surrender of the rights hitherto enjoyed by the non-Jewish communities in Palestine;"
What were those rights? The Mandate preserved the civil and religious rights of the local Arabs but did not create any political rights for them. The civil rights included individual political or electoral rights but not the collective political right of self-determination. It did not and could not "preserve" any collective political rights or "national rights" in Palestine for local Arabs in Palestine as they had never in history had any. It follows, therefore, as to political rights, the local Arabs were no worse off than they were under the Ottoman rule from 1520 to 1920, the British suzerainty from 1920 to 1948, or the Jordanian rule from 1948 to 1967.
But the Arabs didn't want the Jews to have any land with political rights for religious reasons, because it violated Islam to have any inroads on the Dar-al-Islam. They engaged in jihad against the Jews and the Arab Higher Committee brought in the Armies of the surrounding Arab and Muslims States.
What was the effect of the abandonment of the trust by the trustee in 1948? Howard Grief provides a more legally precise reason, but a simple way to look at it was that when the trustee quit his obligation, the only equitable thing to do was to give the rights to the beneficiary of the trust or the ward of the guardian.
Going back to 1922, by 1922 the British Government's interests had changed and the government had changed. In addition to its problems with the deposing of King Feisal, it was defending itself from charges that it had conferred political rights to the same land to the French, the Arabs and the Jews in three different agreements, the Sykes-Picot agreement, the McMahon-Hussein correspondence, and the Lord Balfour Declaration. So in 1922, Churchill, in a White Paper, tried wiggle out of England's obligation to the Jews by hinting broadly that a "national home" was not necessarily a state. However in private, many British officials agreed with the interpretation of the Zionists that a state would be established when a Jewish majority was achieved.
In the British cabinet discussion during final consideration of the language of the Balfour Declaration, in responding to the opposition of Lord Curzon, who viewed the language as giving rise to the presumption that Great Britain favored a Jewish State, Lord Balfour stated: "As to the meaning of the words 'national home', to which the Zionists attach so much importance, he understood it to mean some form of British, American, or other protectorate, under which full facilities would be given to the Jews to work out their own salvation and to build up, by means of education, agriculture, and industry, a real center of national culture and focus of national life. It did not necessarily involve the early establishment of an independent Jewish State, which was a matter for gradual development in accordance with the ordinary laws of political evolution." The key word here was 'early'; otherwise, the statement makes it quite clear that Balfour envisaged the eventual emergence of an independent Jewish state. Doubtless he had in mind a period somewhat longer than a mere thirty years; but the same could also be said of Chaim Weizmann."
According to Lloyd George, one of Churchill's contemporaries, for example, the meaning was quite clear:
"There has been a good deal of discussion as to the meaning of the words "Jewish National Home" and whether it involved the setting up of a Jewish National State in Palestine. I have already quoted the words actually used by Mr. Balfour when he submitted the declaration to the Cabinet for its approval. They were not challenged at the time by any member present, and there could be no doubt as to what the Cabinet then had in their minds. It was not their idea that a Jewish State should be set up immediately by the Peace Treaty without reference to the wishes of the majority of the inhabitants.
On the other hand, it was contemplated that when the time arrived for according representative institutions to Palestine, if the Jews had meanwhile responded to the opportunity afforded them by the idea of a National Home and had become a definite majority of the inhabitants, then Palestine would thus become a Jewish Commonwealth. The notion that Jewish immigration would have to be artificially restricted in order to ensure that the Jews should be a permanent minority never entered into the heads of anyone engaged in framing the policy. That would have been regarded as unjust and as a fraud on the people to whom we were appealing."
If there is any further doubt in the matter, Balfour himself told a Jewish gathering on February 7,1918: "My personal hope is that the Jews will make good in Palestine and eventually found a Jewish state. It is up to them now; we have given them their great opportunity." 
Following an opinion of the renowned international lawyer Julius Stone that focused on the settlement question, President Reagan and succeeding Presidents through George W. Bush maintained a US view that the Jewish Settlements in the West Bank were legal but as a policy matter should be discouraged because of their tendency to discourage the Peace Process. President Obama while continuing the position on policy has not specifically stated his view on legality of the settlements but has referred to them as “illegitimate”..
As to Jerusalem, East Jerusalem fell in 1948  to an attack of the Arab Legion supplied and trained by the British and led by Sir John Bagot Glubb frequently referred to as "Glubb pasha". The Arab Legion later became the Jordanian Army.
The Jordanians demolished 58 synagogues and their contents, uprooted the tombstones of Jewish cemeteries, and used them for paving or building latrines, and built a latrine against the Western Wall of the Temple Mount, the single most holy site for Jews. They expelled all the Jewish inhabitants of East Jerusalem and it became, as Adolph Hitler liked to say, judenrein or cleansed of Jews. In 1967 in the Six Day War, Israel drove the Jordanians east to the Jordan River and became in control of East Jerusalem. They did not use their conquest to deprive the Moslems access to their holy sites in East Jerusalem as the Jordanians had done to the Jews and Christians.
Has the UN's Partition Plan any remaining significance for either the Arabs or the Jews?
No. According to acclaimed International Lawyer Julius Stone, ""The State of Israel is … not legally derived from the partition plan, but [in addition to the grants referred to above] rests (as do most other states in the world) on A. assertion of independence by its people and government, B. on the vindication of that independence by arms against assault by other states, and C. on the establishment of orderly government within territory under its stable control." The Partition plan had assigned the Jerusalem Metropolitan Area to the UN's International Control, at least temporarily for a period of 10 years. However in the war of 1948, the UN did nothing to vindicate that assignment by force of arms against the assault of the surrounding Arab states. Therefore nothing remains of that part of the Partition Plan either. 
In fact you read in the news and hear on TV a lot about Jewish settlements outside of Jerusalem and in East Jerusalem, but have you ever seen or heard a reference to new Arab settlements there? Since 1950 more than twice as many new settlements have been built by Arabs in the West Bank as have been built by Jews, totally ignored by the press. They fill them with Lebanese, Iraqis, Jordanians and Egyptians, and, mirabile dictu, they are Palestinians. An Israeli Professor in Haifa named Steven Plaut suggests, tongue in cheek, that the Arabs must have changed the name of the area from Judea and Samaria to the "West Bank" so they wouldn't look silly in claiming that the Jews were illegally settling in eponymous Judea.
In June,1967, in the Six Day War , Israel recaptured Judea, Samaria and East Jerusalem. In 1994 Israel agreed that in return for a quitclaim of Jordan, to CisJordan, or the land of Palestine west of the Jordan River, it would release its claim to TransJordan, the land East of the Jordan to the Hashemite Kingdom of Jordan. 
My understanding from many authors, is that the Arab claims for the Arab population in Judea, Samaria and East Jerusalem are overstated. Annexing the so called West Bank would not currently jeopardize a Jewish democracy in Israel. Nor would it in the long run as correct population growth shows Jewish population increase in the West Bank greater than that of the Arabs.
I would only offer citizenship to those, Muslim, Jewish or Christian, who would take a loyalty oath to Israel. Others could remain with the status of permanent residents.
What about Gaza? It it were to keep shooting missiles at Israel, that would be a casus belli and Israel should take it over. Also, when it ceded its sovereignty over Gaza to the Arabs living there, the cession was under a tacit agreement that the Arabs would quit their attacks on Israel. They haven't.  A material breach of that obligation also justifies a takeover. Although the people in Gaza were ceded Israel’s political or national rights to the Gaza Strip, they never met the requirements for sovereignty
The first of these is: are the Arabs local to Palestine a “people”? No, as noted above they are an invented people. Another requirement of a separate nation-state is unified control. When armed truces were broken by the Gazans, Hamas, that claims control, always blames the problem on other terrorist organizations. Since Israel’s takeover would not be taking land of another sovereign, the land would not be occupied, but disputed with Israel having the far better claim. I would suggest that until further Jewish population increase over that of the non-Jewish population justifies annexation of Gaza, that the Gazans be authorized Home Rule, but no vote in Israel’s policies.
Israel should retain the right to eliminate candidates or parties that are terrorists. That should meet the requirements of the French "procès verbal" as the Arabs in Gaza never had the right to vote on the policies of the Ottoman Empire.
In sum, it appears that there are five separate views that justify Israeli sovereignty over CisJordan. These are
1. The San Remo Resolution of 1920 which is justification under International Law,
2. The Anglo-American Convention of 1924 makes the Balfour Policy Treaty law and therefore the Domestic Law of the US and the UK,
3. Facts occurring after 1948, including Jordan’s aggressive war in invading a land in which the Jews had been awarded political rights, and the defensive war by the Jews retaking it resulted in acclaimed International Lawyers holding that the West Bank was disputed, not occupied, and the Jews had the better claim to it.
In the Partition of 1947, the UN General Assembly recommended an award of part to the Arabs, that was not a grant because it had already been granted to the Jews. The Jews assented, but the Arabs declined. The Jews still had their rights under San Remo. The Arabs had no rights, certainly not the inalienable rights continuously claimed by Arafat and Abbas.
4. In 1948 Israel declared independence, established unified control over its territory and defended it by blood and treasure. That is historically the way sovereignty arises.
5. Under canon law the Jews had exclusive rights granted by G-d as provided in the Old Testament.
These San Remo rights make possible a one state solution to the current Arab Israeli conflict in Palestine. Those in the Diaspora are also intended as the beneficiaries of the San Remo grant. However in writing this from the relative safety of suburban Washington, DC, it is not our intention to urge this course on the heroic Israelis who currently face an added existential threat from Iran. Note we say relative safety.
With Iran’s hurrying development of nuclear bombs and intercontinental ballistic missiles, no one is safe. This is only to confirm the necessity and legality of a "one Jewish state solution" that others, before us, have already suggested. It is the Israelis who must choose.
Mr. Salomon Benzimra contributed to this article. He is the author of "The Jewish People's Rights to the Land of Israel", available in "Amazon-Kindle edition".
 Mandate Article 5 http://www.mtholyoke.edu/acad/intrel/britman.htm
 Article 15. It is preserved by Article 25
 Text of San Remo Resolution, section (a) I am advised it appears only in two paragraphs of the Agreement, written in French
 http://islamizationwatch.blogspot.com/2009/03/what-does-dar-al-harb-dar-al-islam-dar.html Spain in the dar al Harb http://countercultureconservative.wordpress.com/2010/04/02/dar-al-islam-muslim-worshippers-squat-spanish-cathedral/
 Grief refers to the doctrine of "acquired rights" codified in the Vienna Convention on the Law of Treaties, Article 70 Article 70 1 b) and the legal doctrine of "estoppel" See: Grief at pp.175,176 (The Legal Foundation and Borders of Israel under International Law)
 High Walls of Jerusalem, at 611
 David Lloyd-George, Memoirs 736-7.
 “Israel and Palestine: An Assault on the Law of Nations” which dealt with the legal aspects of the Arab-Israeli conflict. In it, Stone set forth the central principles of international law upon which Israel’s right to settle the West Bank is based and discussed the inapplicability of Article 49(6) of the Fourth Geneva Convention to the case of Israeli settlement.
Stone drew upon the writings of Professor Stephen Schwebel, former judge on the Hague’s International Court of Justice (1981-2000), who distinguished between territory acquired in an "aggressive conquest" (such as Japanese conquests during the 1930s and Nazi conquests during World War II) and territory taken in a war of self-defense (for example, Israel’s capture of the West Bank and the Gaza Strip in 1967 war). He also distinguished between the taking of territory that is legally held by another nation (such as the Japanese occupation of Chinese territory and the Nazi Germany occupation of France, Holland, Belgium and other European lands) as opposed to the taking of territory illegally held. The latter applies to the West Bank and Gaza, which were not considered the legal territories of any High Contracting Party when Israel won control of them; their occupation after 1948 by Jordan and Egypt was illegal and neither country ever had lawful or recognized sovereignty. The last legal sovereignty over the territories was that of the League of Nations Palestine Mandate which encouraged Jewish settlement of the land. See also a discussion of Stone's work, by Andrew Dahdal: “A Reflection On The Views Of Julius Stone And The Applicability Of International Law To The Middle East Israel and Palestine: An Assault on the Law of Nations” which dealt with the legal aspects of the Arab-Israeli conflict. Finally, see a video with Danny Ayalon, Deputy Foreign Minister of Israel, adopting and illustrating the position of Stephen Schwebel and Julius Stone.
 http://www.jcpa.org/JCPA/Templates/ShowPage.asp?DBID=1&LNGID=1&TMID=111&FID=443&PID=0&IID=3052 http://en.wikipedia.org/wiki/Western_Wall
 Draft Report of Arab Settlement Activity in the West Bank http://www.eretzyisroel.org/~jkatz/settlementreport.html
 Best account is still Michael B. Oren, Six Days of War: June 1967 and the Making of the Modern Middle East (2003) See also, his Power, Faith, and Fantasy: America in the Middle East: 1776 to the Present
 Israel - Jordan, Treaty of Peace http://www.mfa.gov.il/MFA/Peace%20Process/Guide%20to%20the%20Peace%20Process/Israel-Jordan%20Peace%20Treaty
 http://www.biu.ac.il/Besa/perspectives15.html http://www.ijn.com/columns/view-from-denver/2220-the-myth-of-the-palestinian-arab-womb
 660 rockets and 404 mortar shells fired into Israel since the end of Operation Cast Lead until the end of February, 2012.
March 1, 2012 Palestinians fired three rockets toward Ashkelon. The projectiles landed in the Ashkelon Coast Regional Council, causing no injuries or damage.
March 2, Palestinians fired a Qassam rocket into the Eshkol Regional Council, causing no injuries or damage., March 3
After nightfall, Palestinians fired a Qassam rocket into the Eshkol Regional Council, causing no injuries or damage, March 4. Palestinians in the Gaza Strip fired two Qassam rockets at Israel. One exploded in the Sdot Negev Regional Council