Controversial Dakota Access Pipeline Case Back in Court

— -- The saga over a $3.7 billion crude oil pipeline that has pitted Native American groups against big oil was back in court today.

At stake is whether the Dakota Access Pipeline will be allowed to traverse what many Native American groups say are sacred ancestral lands.

The case has garnered national attention and hundreds of people are still camped out in protest of the pipeline near the Standing Rock Sioux Tribe's reservation in North Dakota.

The tribe and the pipeline company are awaiting a ruling, which could come as early as this afternoon, from the U.S. Court of Appeals for the D.C. Circuit, which oversaw the appeal being heard today to seek a temporary restraining order against the pipeline's construction.

Today's hearing is part of a legal battle that has continued for months. In the process, it has united Native American groups and environmental activists from across the country, growing into one of the biggest Native American demonstrations in decades.

Even President Obama weighed in on the movement last week at the White House Tribal Nations Conference, telling a crowd featuring more than 500 Native American leaders, “I know many of you have come together, across tribes and across the country, to support the community at Standing Rock and together you’re making your voices heard.”

The fight to block the pipeline began in July, when the Standing Rock Sioux Tribe sued to block the pipeline, arguing they were never meaningfully consulted before construction began. The tribe added that the pipeline ran through what they deemed to be culturally sacred sites and presented a danger to the reservation's water supply.

The pipeline company and the Corps argued in court documents that they followed a standard review process.

The CEO of Energy Transfer, the Texas-based company building the pipeline, denied the tribe's allegations in an internal memo to staff, previously provided to ABC News by the company when asked for comment on the issue last month.

Energy Transfer CEO Kelcy Warren wrote that "concerns about the pipeline’s impact on the local water supply are unfounded," and that "multiple archaeological studies conducted with state historic preservation offices found no sacred items along the route."

Energy Transfer did not immediately respond to ABC News' request today for further comment.

A federal judge denied the tribe's request to temporarily halt construction of the pipeline last month, but the Department of Justice, Department of the Army, and Department of the Interior intervened in an unprecedented manner with a joint statement requesting "that the pipeline company voluntarily pause all construction activity within 20 miles east or west of Lake Oahe."

Tribal leaders viewed the joint statement from the three federal agencies as a temporary victory, but still appealed the judge's ruling in order to make the request for a "voluntary pause" an enforceable court order, bringing them back to court today.

After today's hearing, Chairman Dave Archambault II of the Standing Rock Sioux Tribe spoke at a news conference to highlight the significance of the legal battle.

"Millions of people across the country and world, more than 300 federally recognized tribes, members of Congress and dozens of city governments across the country, stand with the Standing Rock Sioux Tribe in opposition to the Dakota Access Pipeline," Archambault said. "We stand together in peaceful prayer and solidarity because this pipeline threatens the lives of the more than 17 million people who rely on the Missouri River for their water. This pipeline has already destroyed the burial places of our Lakota and Dakota ancestors. If construction continues, our people stand to lose even more of our sacred places and cultural objects."

Archambault went on to say that the Obama administration and the federal government have a responsibility to uphold the "treaty rights of the Standing Rock Sioux Tribe."

"The U.S. Army Corps of Engineers approved the pipeline without consulting with our tribe. The approval of this pipeline by the U.S. Army Corps of Engineers is a violation of our treaty rights and we will not stop fighting until our lands, people, water and sacred places are permanently protected," Archambault added.

The appeals court previously issued a temporary administrative injunction restricting construction for 20 miles on both sides of Lake Oahe last month, according to lawyers representing the tribe, and this temporary halt will remain in place pending the court's decision.

Other than the small area near the reservation, the 1,172-mile, four-state pipeline is nearly complete, according to The Associated Press.