Though President Trump signed an Executive Order this week to expedite the construction of the Dakota Access pipeline, James Boasberg, a Federal judge, has ruled that the U.S. Army Corps of Engineers should begin with a full environmental study of the disputed crossing of the Missouri River in North Dakota.

The decision effectively prevents Energy Transfer from proceeding with construction of the pipeline until the environmental study is completed. The study could take up to two years, but the study notice can be withdrawn if Boasberg were to eventually rule that ETP has permission for the crossing, Army attorneys said.

The Standing Rock Sioux and its supporters believe the four-state pipeline threatens drinking water and cultural sites.

The tribe issued a statement Wednesday saying the study is "yet another small victory on the path to justice."