According to Jacques Gauthier, an expert in international law, “The San Remo resolutions adopted by the Principal Allied Powers on April 25, 1920, established the territorial rights of the Jewish People under international law in respect to Palestine. The sovereignty entitlements granted by the historic San Remo Conference of 1920 remain in force to support the legal claims to the lands for the State of Israel and the Jewish People. Regardless of what may be negotiated by the parties involved in the territorial Israeli-Palestinian conflict, the starting point must be what is historically true in international law.”

The Arab state of Trans-Jordan was established by the British government in 1921, within the boundaries of the Palestine Mandate that was originally allotted for the Jewish National Home, and the Council of the League of Nations approved the partition of Palestine in 1922. Gauthier says that Israel arguably relinquished its claim over areas of Palestine east of the Jordan River, when it signed a peace treaty with Jordan in 1994. But he points out that the remaining lands west of the Jordan River remain the property of the Jewish People under international law.

http://www.cjnews.com/perspectives/forgotten-history-gained-san-remo

See also Palestine, Uti Possidetis Juris and the Borders of Israel