This is not an accurate representation. Jewish people were given the legal ability to purchase land in Mandatory Palestine. The vast majority of Palestinian Arabs were tenant farmers or landless labourers. Jewish land purchases inevitably led to the displacement of these tenants, but this was the lawful outcome of a lawful land sale.
https://en.wikipedia.org/wiki/Jewish_land_purchase_in_Palest...
The issues surrounding occupation of land after the 1948 and 1967 wars are significantly more complex and arguably do involve violations of international law by Israel.
If I sell you my land, does that make it right for you to form a separate state with it? Perhaps I would rethink that decision with the advance knowledge of your intentions.
https://en.wikipedia.org/wiki/End_of_the_British_Mandate_for...
The majority of land purchases were made by the Jewish National Fund. Their aspiration to form a state was explicit and overt.