Many of us, in the name of seeking a lasting middle eastern peace treaty, have long wondered whether Israel could negotiate such a peace by agreeing to give up all the land they have occupied since their decisive victory in the war of 1967. They offered to give up that land then, in exchange for peace and recognition by their Arab neighbours of Israel's right to exist, but their offer was rejected.
Those who think Israel can "buy" peace by giving up those territories should read this.
...[I]n 1967, Egypt, Syria and Jordan again attacked Israel, again with the repeated announcement that the objective was its "annihilation." Israel turned the tables and won the war. Soon after that victory, Israel offered the Arabs to hand them all the territory it had regained, in return for peace. At a conference in Khartoum the unanimous Arab reply was: No negotiations. No peace. No recognition....[h/t to BenS]
It was shortly afterward that the movement of Jewish settlers was launched. It is noteworthy that the last defining document that underwrites the legality was the Geneva Convention of 1949. It dealt with occupied territories. Its second clause, stating its scope, makes it clear that it does not apply to the Jewish presence in Judea and Samaria - because Jordan was not a sovereign possessor but an illegal invader, and similarly was Egypt an illegal invader of Gaza. Israel liberated both areas, restoring them to the territory of the Palestine Mandate of 1922.
From the point of view of international law these settlers are as legal as any resident of Manhattan or of Shreveport, Louisiana.