Sparing Energy Transfer LP’s Dakota Access Pipeline (DAPL) from further regulatory headaches, the U.S. Army Corps of Engineers has reportedly decided not to take action to enforce the crude oil line’s vacated easement to cross under Lake Oahe.

DAPL’s crossing of the large reservoir, behind the Oahe Dam on the Missouri River that begins in central South Dakota and continues north into North Dakota, has proved controversial, drawing legal challenges from the Standing Rock Sioux Tribe.

Last year, Judge James Boasberg of the U.S. District Court of the D.C. Circuit found that the Army Corps had violated the National Environmental Policy Act by giving an easement to DAPL for the Lake Oahe crossing. Boasberg ordered the agency to draft an Environmental Impact Statement (EIS); the...