Mysterious political forces emerged in the form of a well-organized protest two years later, in October of 2016, when rioters gathered near the unfinished portion of pipeline that is nearest to the Standing Rock Indian Reservation on the North Dakota border. At no point does the DAPL cross the Standing Rock Indian Reservation. Indeed, the Corps found DAPL to pose no environmental threat and the states lead archeologist declared that there were neither cultural sites nor sacred burial grounds in the pipelines path. Oddly, even CNN confirmed that very few of the protesters were indigenous Standing Rock tribe members. Most of the protesters were non-Indian out-of-towners from states like California and Arizonaand from countries as far away as Australia, Japan, Serbia and Russia. When Standing Rock tribe members voted on whether to welcome protesters onto their reservation, build permanent structures, and stay through the winterthe tribal community voted with a loud No. 88 members voted: 66 votes were no; the majority of the remaining votes were undecided; and less than 10 votes were yes. The Corps met with 55 tribes 389 times and exclusively with the Standing Rock Sioux a dozen times for input! Most global leaders who condemned DAPL incorrectly assumed the oil pipeline endangered the environment or hurt ancestral lands of indigenous peoples. Source: https://townhall.com/columnists/katiekieffer/2017/02/27/dapl-resistance-the-real-story-n2291072
It was never about the environment, it's all about fossil fuels. If they cared about the environment, they would not have left literally tons of human excrement, trash, and litter at their camp site.