By Jack Healy and Nicholas Fandos, New York Times–

CANNON BALL, N.D. — The Standing Rock Sioux Tribe won a major victory on Sunday in its battle to block an oil pipeline being built near its reservation when the Department of the Army announced that it would not allow the pipeline to be drilled under a dammed section of the Missouri River.

The Army said it would look for alternative routes for the $3.7 billion Dakota Access pipeline. Construction of the route a half-mile from the Standing Rock Sioux reservation has become a global flash point for environmental and indigenous activism, drawing thousands of people out here to a sprawling prairie camp of tents, tepees and yurts.

“The best way to complete that work responsibly and expeditiously is to explore alternate routes for the pipeline crossing,” Jo-Ellen Darcy, the Army’s assistant secretary for civil works, said in a statement. The move could presage a lengthy environmental review that has the potential to block the pipeline’s construction for months or years.

But it was unclear how durable the government’s decision would be. Sunday’s announcement came in the dwindling days of the Obama administration, which revealed in November that the Army Corps of Engineers was considering an alternative route. The Corps of Engineers is part of the Department of the Army.

President-elect Donald J. Trump, however, has taken a different view of the project and said as recently as last week that he supported finishing the 1,170-mile pipeline, which crosses four states and is almost complete.

Though the Army’s decision calls for an environmental study of alternative routes, the Trump administration could ultimately decide to allow the original, contested route. Representatives for Mr. Trump’s transition team did not immediately respond to requests for comment.

Mr. Trump owns stock in the company building the pipeline, Energy Transfer Partners, but he has said that his support has nothing to do with his investment.

There was no immediate response from Energy Transfer Partners, but its chief executive, Kelcy Warren, has said that the company was unwilling to reroute the pipeline, which is intended to transport as much as 550,000 barrels of oil a day from the oil fields of western North Dakota to a terminal in Illinois.


The Conflicts Along 1,172 Miles of the Dakota Access Pipeline

A detailed map showing the Dakota Access Pipeline that has led to months of clashes near the Standing Rock Sioux Reservation in North Dakota.


Reaction was swift on both sides, with environmental groups like Greenpeace praising the decision. “The water protectors have done it,” a Greenpeace spokeswoman, Lilian Molina, said. “This is a monumental victory in the fight to protect indigenous rights and sovereignty.”

But Craig Stevens, a spokesman for the MAIN Coalition, a pro-infrastructure group, condemned the move as “a purely political decision that flies in the face of common sense and the rule of law.”

“Unfortunately, it’s not surprising that the president would, again, use executive fiat in an attempt to enhance his legacy among the extreme left,” Mr. Stevens said in a statement. “With President-elect Trump set to take office in 47 days, we are hopeful that this is not the final word on the Dakota Access Pipeline.”

Representative Kevin Cramer, Republican of North Dakota and a Trump supporter, called Sunday’s decision a “chilling signal to others who want to build infrastructure in this country.”

“I can’t wait for the adults to be in charge on Jan. 20,” Mr. Cramer said, referring to Mr. Trump’s inauguration.

Still, the announcement set off whoops of joy inside the Oceti Sakowin camp. Tribal members paraded through the camp on horseback, jubilantly beating drums and gathering around a fire at the center of the camp. Tribal elders celebrated what they said was the validation of months of prayer and protest.

“It’s wonderful,” Dave Archambault II, the Standing Rock tribal chairman, told cheering supporters who stood in the melting snow on a mild North Dakota afternoon. “You all did that. Your presence has brought the attention of the world.”

The decision, he said, meant that people no longer had to stay at the camp during North Dakota’s brutal winter. The Corps of Engineers, which manages the land, had ordered it to be closed, but the thousands of protesters had built yurts, tepees and bunkhouses and vowed to hunker down.

“It’s time now that we move forward,” Mr. Archambault said. “We don’t have to stand and endure this hard winter. We can spend the winter with our families.”


Theresa Sandoval, of the Red Willow Tribe in northern New Mexico, bringing firewood back to her North Dakota camp early Sunday morning. CreditAlyssa Schukar for The New York Times

Law enforcement officials and non-Native ranchers in this conservative, heavily white part of North Dakota would like little more than to see the thousands of protesters return home. The sheriff has called the demonstrations an unlawful protest, and officials have characterized the demonstrators as rioters who have intimidated ranchers and threatened and attacked law enforcement — charges that protest leaders deny.

But on Sunday, several campers said they were not going anywhere. They said that there were too many uncertainties surrounding the Army’s decision, and that they had dedicated too much time and emotion to this fight to leave now.

Federal and state regulators had issued the pipeline the necessary permits to proceed, but the Corps of Engineers had not yet granted it a final easement to drill under a stretch of the Missouri River called Lake Oahe.

The Standing Rock Sioux had objected to the pipeline’s path so close to the source of their drinking water, and said any spill could poison water supplies for them and other reservations and cities downstream. They also said the pipeline’s route through what are now privately owned ranches bordering the river crossed through sacred ancestral lands.

News of the government’s denial came after the size of the camp had swelled with hundreds, perhaps thousands, of Native and non-Native veterans who had arrived to support the tribe. As word spread, people who had camped out here for months, sometimes in bitterly cold temperatures, and who had clashed violently with local law enforcement, linked arms and cheered and cried.

They screamed, “Mni wiconi!” — the movement’s rallying cry — which means “Water is life.”

Jon Eagle Sr., a member of the Standing Rock Tribe, said the announcement was a vindication for the thousands who had traveled here, and for the multitudes who had rallied to the tribe’s fight on social media or donated. Millions of dollars in donations and goods have flowed into the camps for months as the tribe’s fight and the scenes of protesters being tear-gassed and sprayed with freezing water stirred outrage on social media. (Law enforcement officials have insisted the entire time that they have acted responsibly and with restraint.)

“I don’t know quite how to put into words how proud I am of our people,” Mr. Eagle said. “And I mean our people. I don’t just mean the indigenous people of this continent. I mean all the people who came to stand with us. And it’s a beautiful day. It’s a powerful day.”

Ken Many Wounds, who has served as a tribal liaison to express concerns and questions to law enforcement, said he had been standing by the camp’s main fire — one that is tended constantly — when he heard the news from the tribal chairman’s wife. He said he did not believe it at first.

“I hugged her, I cried,” he said. “Our prayers have been answered. A lot of people didn’t believe that prayer was going to be the answer. But our people stayed together. In our hearts, we knew.”