In 1947 when they chose to leave. In 1948-1967 when the Arab states controlled 95% of the land that these Arabs want to return to. Wars have consequences, if you initiate a war and lose, you’re not gonna get everything back. That’s the risk of war.

I have no idea what “legally affirmed” means in the context of sovereign states. The UN, or even the UNSC passing something doesn’t actually mean anything as it applies to sovereign nations. Paraphrasing Andrew Jackson: a law is only as good as the ability to enforce it. A bunch of random people agreeing to something even if they call themselves “The United Nations” doesn’t mean anything if that group of friends doesn’t have the will or ability to enforce whatever they’ve agreed to. They’re akin to you and your drinking buddies passing out edicts after one to many dry martinis.