President Barack Obama threw down a gauntlet last weekend: no vote at the United Nations, he asserted, would ever create a Palestinian state.

The Palestinians hope to prove him wrong. But their planned bid for U.N. recognition this fall of a state in the West Bank, Gaza and east Jerusalem — territories occupied by Israel since the 1967 Mideast war — enters largely unknown legal ground, and the Palestinians are still trying to work out how best to work the U.N. labyrinth.