Construction at the Dakota Access Pipeline has come to a halt and protesters have taken their message to Washington D.C.
The U.S. District Court says they won't make a ruling on the issue until after the hearing on September 8th.
Protesters and environmental experts say construction of the pipeline can have a devastating environmental impact.
The Missouri River is the longest river in North America, spanning from Montana all the way to Missouri.
Many people along the way use it for crops and drinking water.
"You know the crops, everything that everybody grows and lives off of and the ecosystem it's all off balance. That water is very holy," says protester Vonda Eagle Horse.
Even though experts say pipelines are considered one of the safer methods of transporting oil, they are still prone to problems.
"It's like any transportation system. Cars crash, planes crash, trains crash... Pipelines will rupture," says Associate Professor of Geography at MSUM Dr. Paul Sando.
That could put crops and the drinking water supply at risk.
"You could not take oil contaminated water and put it on crops. It's not a good idea. By the same token, you wouldn't want oil contaminated water going through your water treatment system either," Sando says.
Not only would an oil spill affect people's drinking water as well as crops, but there is wildlife unique to the Missouri river that would also be in harm's way if a spill were to occur.
"One is the Piping Plover which is a shore bird. It is an endangered species. In terms of fish there is the paddle fish. They are unique to two river systems in the world," says Sando.
A spill would take an intensive cleanup effort and Dr. Sando says oil spills can harm the ecosystem for years.
"Without water nothing will live. Everything on this land water is essential to it," says Protest Leader Virgil Taken Alive.
Dr. Sando says if construction continues, the pipeline will still have to cross the Missouri River, even if it is away from the Reservation.