If Congress hasn't formally voted to declare war or authorize military action against Iran, this resolution would require the President to pull U.S. troops back from any fighting in or against Iran. It's essentially Congress asserting its constitutional say over starting wars, rather than letting the President keep military action against Iran going on his own. One built-in exception: U.S. forces could still act in self-defense if American troops, personnel, or facilities anywhere in the world came under attack — that response wouldn't be blocked by this resolution.