Ayatollah Khamenei says nuclear weapons are 'forbidden under Islamic law'

During tensions with the United States over Iran's nuclear ambitions, Ayatollah Khamenei has come out and declared a fatwa over the use of nuclear weapons. But what does this really mean for Iran and the recent nuclear deal? The World's host Marco Werman speaks with Omid Safi, a professor of Iranian studies at Duke University and the director of the Duke Islamic Studies Center, to find out.