When nation-states default on their national sovereignty, cities have to step up. They can’t wait. And they don’t need to ask for permission. They can exert their own sovereignty. They understand that the local and the global have really, truly come together, that we live in a global, local world, and we need to adjust our politics accordingly. At this moment of extraordinary international uncertainty when our multilateral institutions are paralyzed and our nation-states are in retreat, cities and their leaders are our new 21st century visionaries.