My second day on the Standing Rock Sioux Reservation in the Dakotas, an official from the Bureau of Indian Affairs sent a memo to all its law-enforcement employees forbidding them to talk to me. One of those officers working the jail at Fort Yates, North Dakota, walked into a tribal judge’s office, and throwing the memo down, said, “Can you believe this shit?” Since I was on the reservation to write about crime—sexual assault and rape, in particular, and how often these crimes go unreported when they take place on tribal land—I had naturally hoped to speak to the…