Tex G. Hall, the three-term tribal chairman on this remote, once impoverished reservation, was the very picture of confidence as he strode to the lectern at his third Annual Bakken Oil and Gas Expo and gazed out over a stuffed, backlit mountain lion.
Tall and imposing beneath his black cowboy hat, he faced an audience of political and industry leaders lured from far and wide to the “Texpo,” as some here called it. It was late April at the 4 Bears Casino, and the outsiders endorsed his strong advocacy for oil development and the way he framed it as mutually beneficial for the industry and the reservation: “sovereignty by the barrel.”
“M.H.A. Nation is No. 1 for tribal oil produced on American soil in the United States right now currently today,” Mr. Hall proudly declared, referring to the Mandan, Hidatsa and Arikara Nation.
But, in a hall decorated with rigs and tepees, a dice throw from the slot machines, Mr. Hall’s self-assurance belied the fact that his grip on power was slipping. After six years of dizzyingly rapid oil development, anxiety about the environmental and social costs of the boom, as well as about tribal mismanagement and oil-related corruption, had burst to the surface.
By that point, there were two murder cases — one person dead in Spokane, Wash., the other missing but presumed dead in North Dakota — tied to oil business on the reservation. And Mr. Hall, a...