“Out here, it feels like we’re in our own world. It doesn’t feel like the U.S. It feels like a third-world country.”
Harold Frazier said Trump should also apologize to the nation for his Pocahontas remarks.
The #NoDAPL movement drew worldwide attention as protestors and police descended on North Dakota.
Opponents quickly outlined plans for lawsuits, political pressure and street action.
“You can’t drink oil. Keep it in the soil," marchers chanted.
Authorities say they arrested 46 people during their second day raiding Oceti Sakowin.
A few protesters who refused to leave remained at the site Thursday.
“As much as this is an ecological crisis, it is a moral failing of our society," one protester said.
The decision, a defeat for environmentalists and the Standing Rock Sioux, is likely to be challenged.