This resolution says the President must pull U.S. military forces out of any combat involving Iran unless Congress has actually voted to declare war or specifically authorize that military action. In other words, if the President wants to keep U.S. troops fighting in or against Iran, he'd need Congress's formal sign-off first, rather than acting alone. There's one exception built in: this wouldn't stop the military from responding if the U.S., its troops, or its facilities anywhere in the world came under attack — self-defense is still allowed regardless of Congress's involvement.