With a court decision looming, and the National Guard on hand, a tribe protesting an oil pipeline from North Dakota said it was calling for peace.

The Standing Rock Sioux Tribe took notice of a decision from North Dakota Gov. Jack Dalrymple to call in the state National Guard to assist state and county police in managing crowds protesting the construction of the Dakota Access pipeline.

Tribal Chairman David Archambault II said the pipeline poses a threat not only to sacred sites, but to the millions of people who depend on the Missouri River for water.

"We call upon all water protectors to greet any decision with peace and order," he said in a statement. "Even if the outcome of the court's ruling is not in our favor, we will continue to explore every lawful option and fight against the construction of the pipeline."

Archambault earlier this week expressed disappointment in a temporary halt to the construction of part of the pipeline. A court is expected to issue findings later Friday on the merits of tribal challenges to the Dakota Access pipeline.

Tribal groups are suing federal regulators over permits for the 1,134-mile pipeline because of threats to the Missouri River and other regional water ways. The U.S. Army Corps of Engineers, which examined separately each water crossing, is accused of sidelining tribal interest.

The Army Corps said it has no objections to the temporary order, but said the merits of the challenge were unlikely to stand.

In a letter to President Obama, tribal and environmental groups said the oil pipeline from North Dakota poses a threat to their existence.

The protest has sparked attention from current and former U.S. presidential candidates. Sen. Bernie Sanders, I-Vt., put Dakota Access on the same footing as Keystone XL oil pipeline, which the White House denied in part on environmental grounds.

At its peak, Dakota Access would transport about half of the oil that North Dakota produces per day, or around 570,000 barrels per day. Much of the oil leaving North Dakota now does so by rail, a transport method also under scrutiny because of deadly derailments in past years.

Energy Transfer Partners, the group behind the project, has already started soliciting commitments to help transport North Dakota oil through the system.