For 65 years, even as India and Pakistan fought wars, severed diplomatic ties and traded nuclear threats, one agreement held: the Indus Waters Treaty, which governs the river system sustaining roughly 300 million people across the subcontinent.That was until April last year, when New Delhi suspended the pact in the aftermath of a deadly militant attack on tourists in Kashmir that it blamed on Islamabad.Now, an international tribunal has ruled that it should have done no such thing – handing...