ROSEBUD INDIAN RESERVATION, S.D. — In early 2010, the South Dakota government gave its blessing to a Canadian company seeking to move crude oil in a pipeline beneath the American heartland. Opposition had been minimal.

“We didn’t know about it,” said Faith Spotted Eagle, the chairwoman of the Yankton Sioux Tribe’s treaty council. “It was real swift and quiet.”

But in the years since, the proposed pipeline, known as Keystone XL, has become the object of a national debate, and Ms. Spotted Eagle has emerged as a leader of an increasingly organized coalition of Native Americans, landowners and grass-roots groups seeking to block its construction in this state and elsewhere. So much time has elapsed that the 2010 construction permit is now up for recertification, requiring a new round of hearings expected to pit South Dakota activists against pipeline supporters eager for construction to begin.

“These kinds of things in history have been more procedural in nature,” said Mark Cooper, a spokesman for TransCanada, the company proposing Keystone XL. “But I think the new reality is that opponents of the pipeline will do anything they can do to slow progress.”