GOLDEN VALLEY, Minn. -- For eight months, protesters have camped along the Missouri River in North Dakota to fight the construction of the Dakota Access oil pipeline that would run near the Standing Rock Sioux Reservation.

Last week, the Army Corps of Engineers served an order to demonstrators to leave the closed federal land by Monday, Dec. 5.

But those in the camp say—according to a 165-year-old treaty with the Sioux—the camp and the pipeline are on ancestral tribal land.

So is it federal land or Sioux land? Depends how you see it.

“The pipeline today, if you talk to federal officials in the U.S., is running on federal land and private land, not running in the boundaries of the Sioux tribe’s reservation,” said Professor Colette Routel, co-director of the Indian Law Program at Mitchell Hamline School of Law.

A look at a current map shows the proposed pipeline passing about a half-mile north of the Standing Rock Sioux reservation.

But another map of the reservation after the 1851 Treaty of Ft. Laramie between the U.S. government and nine Indian tribes shows the pipeline cuts clearly through the middle of this boundary.

And here is why many protestors feel the land does in fact still belong to the Sioux.

The lines of the reservation started changing without Sioux approval in the mid-1800s after gold was found in the Black Hills, according to Routel.

“The government, in particular Congress, passed a number of statutes unilaterally that altered the boundaries of the reservation and confiscated that land,” said Routel. “The U.S. Supreme Court later issued a decision saying that the government acted unlawfully when it did that and awarded the tribes a large sum of money. At the time it was more than $100 million to compensate for the taking of that land, but the tribes have refused to accept payment and instead want the land returned.”

Frank Bibeau is an attorney and executive director of the 1855 Treaty Authority. He has litigated Native American treaty rights in Minnesota.

He cites the U.S. Supreme Court decision in Minnesota v. Mille Lacs Band that gave the Ojibwe Chippewa hunting, fishing and gathering rights on federal land that was sold by the tribe in 1837.

However, Bibeau says the situation for Standing Rock is more ambiguous.

“[The tribe] has to work through the federal government and convince them as well why what they are doing right now is wrong and how and where it should go in another way or if it shouldn't go at all,” said Bibeau.

Bottom line, treaties still matter very much in the eyes of Native American tribes and in the letter of law, but in the instance of Standing Rock Sioux and the Dakota Access pipeline, Routel says, legally, the treaty does not apply.

“It is indisputable that [the protest] is on federal land,” said Routel.