Night falls on Oceti Sakowin Camp on the edge of the Standing Rock Sioux Reservation on December 1, 2016 outside Cannon Ball, North Dakota. Native Americans and activists from around the country have been gathering at the camp for several months trying to halt the construction of the Dakota Access Pipeline. The proposed 1,172-mile-long pipeline would transport oil from the North Dakota Bakken region through South Dakota, Iowa and into Illinois. (Photo by Scott Olson/Getty Images)





Veterans line up for dinner at the Oceti Sakowin camp where people have gathered to protest the Dakota Access oil pipeline in Cannon Ball, N.D., Sunday, December 4, 2016. The U.S. Army Corps of Engineers said Sunday afternoon that the four-state, $3.8 billion Dakota Access oil pipeline cannot be built under Lake Oahe, a Missouri River reservoir where construction had been on hold. (Photo by David Goldman/AP Photo)





In this Thursday, December 1, 2016 photo, Cat Bigney, part of the Oglala Native American tribe, waits on the shore of the Cannonball river for travelers to arrive by canoe at the Oceti Sakowin camp where people have gathered to protest the Dakota Access oil pipeline in Cannon Ball, N.D. So far, those at the camp have shrugged off the heavy snow, icy winds and frigid temperatures. But if they defy next week's government deadline to abandon the camp, demonstrators know the real deep freeze lies ahead. Life-threatening wind chills and towering snow drifts could mean the greatest challenge is simple survival. (Photo by David Goldman/AP Photo)





A group of veterans confront police on Backwater Bridge during ongoing demonstrations against the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 1, 2016. (Photo by Lucas Jackson/Reuters)





Tipis stand in the night inside of the Oceti Sakowin camp as demonstrations against plans to pass the Dakota Access pipeline continue near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 1, 2016. (Photo by Lucas Jackson/Reuters)





A group of veterans confront police on Backwater Bridge during ongoing demonstrations against the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 1, 2016. (Photo by Lucas Jackson/Reuters)





A man holds up a traditional drum during a confrontation between veterans and police on Backwater bridge during a protest against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 1, 2016. (Photo by Stephanie Keith/Reuters)





Veterans have a confrontation with police on Backwater bridge during a protest against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 1, 2016. (Photo by Stephanie Keith/Reuters)





A man rides a horse down a road inside of the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 2, 2016. (Photo by Lucas Jackson/Reuters)





Two campers walk through the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 2, 2016. (Photo by Lucas Jackson/Reuters)





Campers photograph a signpost with the names of various tribes on it inside of the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 2, 2016. (Photo by Lucas Jackson/Reuters)





Waskoness Pitswanakwat, 16, rides her horse in Oceti Sakowin camp during a protest against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 2, 2016. (Photo by Stephanie Keith/Reuters)





A man walks with the flag of an Indian nation in Oceti Sakowin camp during a protest against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 2, 2016. (Photo by Stephanie Keith/Reuters)





Waskoness Pitswanakwat, 16, puts a saddle on her horse in Oceti Sakowin camp during a protest against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 2, 2016. (Photo by Stephanie Keith/Reuters)





Korean War veteran George Martin, 80, an Ojibwe tribe from Hopkins, Michigan, stands with veterans who oppose the Dakota Access oil pipeline on Backwater Bridge near Cannon Ball, North Dakota, U.S., December 2, 2016. (Photo by Terray Sylvester/Reuters)





An opponent of the Dakota Access oil pipeline looks through a scope on the outskirts of the Oceti Sakowin camp near Cannon Ball, North Dakota, U.S., December 2, 2016. (Photo by Terray Sylvester/Reuters)





Three demonstrators greet each other near the entrance of the Oceti Sakowin camp as “water protectors” continue demonstrations against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 2, 2016. (Photo by Lucas Jackson/Reuters)





Campers cook lunch inside of the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 2, 2016. (Photo by Lucas Jackson/Reuters)





A woman from the Tlingit Tsimphean tribe (C) watches the sunrise in Oceti Sakowin camp as "water protectors" continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 3, 2016. (Photo by Stephanie Keith/Reuters)





A woman cries during the sunrise in Oceti Sakowin camp as "water protectors" continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 3, 2016. (Photo by Stephanie Keith/Reuters)





The rising sun illuminates tipis inside the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 3, 2016. (Photo by Lucas Jackson/Reuters)





A camper crosses “flag road” inside the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 3, 2016. (Photo by Lucas Jackson/Reuters)





Tony Dujan plays the trumpet as the sun rises inside the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 3, 2016. (Photo by Lucas Jackson/Reuters)





Healer Angie Spencer uses sage to perform an “energy smudging” ceremony with a veteran inside the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 3, 2016. (Photo by Lucas Jackson/Reuters)





A man makes a sign that reads “vet check in” in Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 3, 2016. (Photo by Stephanie Keith/Reuters)





A sign pointing to the veterans tent is seen in Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 3, 2016. (Photo by Stephanie Keith/Reuters)





A woman stands in a camp behind graffiti of a black snake in Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 3, 2016. (Photo by Stephanie Keith/Reuters)





A painted bus drives on the road past Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 3, 2016. (Photo by Stephanie Keith/Reuters)





A veteran stands in front of homemade shields in Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 3, 2016. (Photo by Stephanie Keith/Reuters)





The sun sets as a helicopter flies over a person using their cell phone near the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 3, 2016. (Photo by Lucas Jackson/Reuters)





Campers stand and watch as members of the National Guard and police departments guard the Backwater Bridge near the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 3, 2016. (Photo by Lucas Jackson/Reuters)





Vehicles and campsites fill the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 3, 2016. (Photo by Lucas Jackson/Reuters)





Veterans work to prepare a large sleeping tent inside of the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 3, 2016. (Photo by Lucas Jackson/Reuters)





Steve Perry from the Odawa tribe displays his Army medal for the camera in Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 3, 2016. (Photo by Stephanie Keith/Reuters)





Horses are seen in a mirror in Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 3, 2016. (Photo by Stephanie Keith/Reuters)





Arvol Looking Horse, spiritual leader of the Sioux nation, participates in a ceremony in Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 4, 2016. (Photo by Stephanie Keith/Reuters)





A man carrying a “Turtle Island struggle eagle staff” stands in Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 4, 2016. (Photo by Stephanie Keith/Reuters)





A man from the Stolo tribe in Canada stands in Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 4, 2016. (Photo by Stephanie Keith/Reuters)





A young Native American man on horseback watches veterans unfurl a flag near the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 4, 2016. (Photo by Lucas Jackson/Reuters)





A woman looks out over the Oceti Sakowin camp as activists celebrate after the Army Corps of Engineers denied an easement for the $3.8 billion Dakota Access Pipeline to continue adjacent to the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 4, 2016. (Photo by Lucas Jackson/Reuters)





A young Native American man rides his horse through the snow near the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 4, 2016. (Photo by Lucas Jackson/Reuters)





A group of veterans gather to eat as snow falls inside of the Oceti Sakowin camp as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline adjacent to the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. December 5, 2016. (Photo by Lucas Jackson/Reuters)





Veterans join activists in a march just outside the Oceti Sakowin camp during a snow fall as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline adjacent to the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 5, 2016. (Photo by Lucas Jackson/Reuters)





Veterans join activists in a march to Backwater Bridge just outside the Oceti Sakowin camp during a snow fall as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline adjacent to the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 5, 2016. (Photo by Lucas Jackson/Reuters)





Veterans join activists in a march to Backwater Bridge just outside the Oceti Sakowin camp during a snow fall as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline adjacent to the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 5, 2016. (Photo by Lucas Jackson/Reuters)





A woman stands on horseback as veterans join activists in a march to Backwater Bridge just outside the Oceti Sakowin camp during a snow fall as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline adjacent to the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 5, 2016. (Photo by Lucas Jackson/Reuters)





Veterans join activists in a march to Backwater Bridge just outside the Oceti Sakowin camp during a snow fall as “water protectors” continue to demonstrate against plans to pass the Dakota Access pipeline adjacent to the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S., December 5, 2016. (Photo by Lucas Jackson/Reuters)





Army veteran Nick Biernacki, of Indiana, prays at Cannonball River at the Oceti Sakowin camp where people have gathered to protest the Dakota Access oil pipeline in Cannon Ball, N.D., December 4, 2016. Tribal elders have asked the military veterans joining the large Dakota Access pipeline protest encampment not to have confrontations with law enforcement officials, adding the group is there to help out those who've dug in against the four-state, $3.8 billion project. (Photo by David Goldman/AP Photo)





Military veterans huddle together to hold a United States flag against strong winds during a march to a closed bridge outside the Oceti Sakowin camp where people have gathered to protest the Dakota Access oil pipeline in Cannon Ball, N.D., Monday, December 5, 2016. (Photo by David Goldman/AP Photo)