Open this photo in gallery: Indian Prime Minister Narendra Modi welcomes Canada Prime Minister Justin Trudeau upon his arrival at Bharat Mandapam convention center for the G20 Summit, in New Delhi, India, on Sept. 9.Evan Vucci/The Associated Press Strained Re “Trudeau accuses India in killing of Sikh leader on Canadian soil” (Sept. 19): There has never been anything like this before. Moving swiftly, on the basis of credible allegations, seems to show Justin Trudeau’s predilection toward a public disclosure sooner rather than later, as if to make amends for previous tardiness in response to foreign interference by China, while also...