OK, let's make this simple. In the late 19th century the Zionists in Europe planned to conquer Palestine and create a Jewish state. That was their intended and stated goal. All during the Mandate period they imported people and weapons in preparation of this planned take over of Palestine. After Resolution 181 was approved, but never implemented by the UN Security Council, the Zionists rolled their troops across Palestine driving unarmed civilians out of their homes. On May 15, 1948 the foreign Jewish Agency that was created in Zurich by the foreign World Zionist Organization declared Israel on land just stolen by force from the Palestinians.
So your point is that international law prohibits the formation of a State in territory where there has been migration of people (even if those people are returning to their indigenous land)? So, Canada is illegal. And the US. Mexico, Brazil, Australia, New Zealand, South Africa, India, Algeria, Pakistan, Barbados, St. Maarten, Angola, Mozambique, all of Latin America, Korea. Even the Ottoman Empire. And it sure screws over Palestine, since they won't be able to permit the migration of "Palestinians" into the territory and still form a State there.