The US Department of the Army announced it will not allow a controversial oil pipeline to be drilled underneath the main water source for the Standing Rock Sioux reservation, dealing an important victory to indigenous and environmentalist protesters who've sought to stop the project.

"It's wonderful," said Standing Rock tribal chairman Dave Archambault II to cheering supporters standing in the North Dakota snow, "You all did that.  Your presence has brought the attention of the world."

Opponents say the Dakota Access oil pipeline would have desecrated sacred sites and put the reservation's only source of fresh water, the mighty Missouri River, at risk.  That half-mile stretch of the US$3.7 Billion dollar project has become a global flashpoint, uniting indigenous groups around the world - including from Australia.  "The best way to complete that work responsibly and expeditiously is to explore alternate routes for the pipeline crossing," said US Army assistant secretary for civil works Jo-Ellen Darcy.

"The water protectors have done it," said Greenpeace spokeswoman Lilian Molina, "This is a monumental victory in the fight to protect indigenous rights and sovereignty."

The move could kick off a renewed environmental impact review that would delay the Dakota Access pipeline's completion for weeks or maybe months.  But it is not clear how long this will last.  US President Barack Obama leaves office in a few weeks, to be replaced by Mr. Conflict-of-interest himself, Donald Trump - who owns stock in the company building the pipeline, Energy Transfer Partners.  The orange clown in the past has claimed that his support for the pipeline has nothing to do with his direct financial interest in seeing it completed. 

Trump's camp has not responded to journalists seeking comment on the latest developments.  But a pro-pipeline development group called the MAIN Coalition invoked Trump's name in condemning the Army:  "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," said spokesman Craig Stevens.

The Army's decision comes as busloads of military veterans arrived to bolster protest camps.  Disgusted by brutal treatment of unarmed, peaceful protesters by local law enforcement and private security goons, the veterans vowed to put their societal status in between the protesters and the rubber bullets, high pressure water cannons in sub-freezing temperatures, and tear gas and pepper spray.