This whole discussion is surreal. But you didn't get my idea and I'll try again. We imagine that Israel and Palestine both give Jerusalem to the UN. Then somebody other than Israel wants to take Jerusalem. Palestine? Could Palestine get an army they thought could hold off Israel? Israel could take all of Palestine, and give Jerusalem to the UN or keep it. If the Palestinians were that stupid it wouldn't get them much. Say it's some other army. Jordan is too weak. Would Jordan agree to let them through? If they want Jerusalem, would they hand it to Palestine and go home or would they keep Palestine and Jordan too? Likely Jordan would fight them. Maybe Palestine would fight them. Meanwhile, would UN invite Israel to defend Jerusalem? Why not? it looks unlikely to me that anybody except Israel could take Jerusalem from the UN, especially since Israel could take it first. And if the UN had Jerusalem then most opponents would not want it as much as if Israel has it.