It is important to remember that the DAPL project is for oil, not Natural Gas. As a result the project does not automatically invoke FERC. Instead, (some) cultural resources are protected because the Corps of Engineers has oversight on water crossings because of the "Waters of the U.S" laws.
Today, as President Trump swore his oath to the office of President the Whitehouse.gov website switched over. The new website removed the pages dedicated to Climate Change and instead, there is now a new page "An America First Energy Plan". This is very relevant to DAPL because this policy position page clearly shows that Waters of the U.S is under direct attack. From https://www.whitehouse.gov/america-first-energy
For too long, we’ve been held back by burdensome regulations on our energy industry. President Trump is committed to eliminating harmful and unnecessary policies such as the Climate Action Plan and the Waters of the U.S. rule. Lifting these restrictions will greatly help American workers, increasing wages by more than $30 billion over the next 7 years.