I did not expect to leave Islamabad thinking about the future of international law. I went to speak. I came home with something harder to shake: a conviction that what is happening on the Indus river is not just a bilateral water dispute between two nuclear-armed neighbours. It is a test of whether the global architecture of treaty-based cooperation can survive the moment we are living in. On June 30, I had the honour of speaking at the Institute of Regional Studies seminar on the Indus Water...