Read Peter's Op-ed on Trump's Immigration Ban in The New York Times The rise of dual citizenship could hardly have been imaginable to a time traveler from a hundred or even fifty years ago. Dual nationality was once considered an offense to nature, an abomination on the order of bigamy. It was the stuff of titanic battles between the United States and European sovereigns. As those conflicts dissipated, dual citizenship continued to be an oddity, a condition that, if not quite...