Critics of pipeline transport of oil cite environmental and land rights issues. Protests over the Keystone XL Pipeline beginning in 2011 and Dakota Access Pipeline have expressed these same concerns. Native peoples have been active protesters. The Standing Rock Sioux of South Dakota opposed the construction plans of the Dakota Access Pipeline because it ran through a symbolically significant area, and expressed concern that it could compromise their source of drinking water. Since pipelines have been built, multiple pipeline accidents have occurred, resulting in oil spills and the contamination of the surrounding environment. The tribe was also not involved in planning the route for the pipeline. These protests also reflect the ongoing struggle for Native American recognition in the United States. In November 2015 President Barack Obama called to stop construction of the Keystone XL Pipeline. In December 2016 the Army Corps of Engineers prevented further construction on the pipeline near the Standing Rock Reservation. On January 24, 2017 President Donald Trump signed an executive order permitting the completion of both the Keystone XL Pipeline and Dakota Access Pipeline. On March 24, 2017 the permit was granted.