News that the federal government ruled against a controversial North Dakota pipeline project was greeted with singing and roars of joy among protesters.
In the Oceti Sakowin camp, native and non-native alike danced to celebratory drumming that blasted through loudspeakers.
But reality soon began to sink in among the thousands who have been fighting the construction of the 1,172-mile Dakota Access Pipeline for months, which the Standing Rock Sioux tribe and others say endangers local drinking water and would disturb sacred tribal sites.
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"You know it's hard to get excited," said Stevey Seymour, a member of the Colville Tribes. Seymour said she was worried the decision could be easily overturned by President-elect Donald Trump's administration.
Here's what may be next for the protesters and Energy Transfer Partners, the Dallas-based company building the pipeline, after the U.S. Army Corps turned down the permit for the project.
What can Trump do?
Trump can overturn Sunday's U.S. Corps decision.
Trump supported the completion of the pipeline, according to an aide's memo recently obtained by the Associated Press. A spokesman, Bryan Lanza, said in the memo that Trump's backing for the pipeline "has nothing to do with his personal investments and everything to do with promoting policies that benefit all Americans."
In general, Trump has pledged to invest in infrastructure projects. During the campaign, he also supported the Keystone XL oil pipeline, which has also prompted opposition.
In an interview with NBC News in November, Energy Transfer Partners CEO Kelcy Warren said he was "100 percent sure that the pipeline will be approved by a Trump administration."
"I believe we will have a government in place that believes in energy infrastructure," he said.
In June, Warren donated $100,000 to the Trump Victory Fund, a joint fundraising committee for Trump's campaign, and a further $3,000 directly to the Trump campaign. For his part, Trump's campaign financial disclosure forms revealed the President-elect's investments totaling between $500,000 and $1 million in Energy Transfer Partners.