Proposed oil pipelines routinely spark protests and intense debate as they wind their way through the government approval process at the local, state, and national levels. However, a pipeline project planned to be completed by the end of 2016 raises new challenges when protesters are supported by members of Congress who misunderstand the necessary approval process.

On September 29, a group of 19 members of Congress sent a letter to President Obama urging him to move to stop the construction of the Dakota Access Pipeline in North Dakota. This pipeline would run from the Bakken oil fields in North Dakota through South Dakota, Iowa, and Illinois, before connecting with a preexisting pipeline which would transfer the crude oil to refineries on the Gulf Coast.

In the letter, the members of Congress echoed the concerns of the Standing Rock Sioux tribe, which alleges that a portion of the pipeline, which runs through land owned by the Army Corps of Engineers near the reservation, threatens historic and sacred sites. The tribe also expressed concern that allowing the pipeline to pass under the Missouri River upstream of the reservation could contaminate drinking water. The members urged the Obama to withdraw permits for the pipeline construction and to force a “comprehensive environmental review with rigorous and meaningful tribal consultation.”

The letter comes at a time of battling directives. On September 9, a statement issued by the Department of Justice, the Department of the Army, and the Department of the Interior acknowledged the tribes’ concerns as “important” and ordered the Army not to authorize construction on the Corps land.

Earlier that day, the U.S. District Court for the District of Columbia denied a motion to halt the pipeline construction. (While the bulk of the construction is on private land, three percent of the project runs across Corps land and is subject to federal permitting.)

The letter mischaracterizes the efforts made by the Corps and Dakota Access to involve the tribe in the pipeline planning process. Documents from the district court case show that the Corps repeatedly made efforts to involve the Standing Rock Sioux and other area tribes in the pipeline planning process, but found their efforts stymied by a lack of cooperation.

The court’s opinion undercuts the letter’s claims that the tribe was ignored by the Army Corps of Engineers during the development of the pipeline route and the permitting process. Instead, at each stage of the process, the Corps and Dakota Access sought to minimize the impact of the new construction.

In North Dakota alone, the pipeline route was modified to avoid 140 of 149 sites with “the potential presence of historic properties,” as identified by a team of professionally licensed archaeologists who surveyed the proposed route. Additionally, the route follows preexisting utility lines, where the ground had been disturbed in the past and new construction was unlikely to damage any undiscovered sites.

Undercutting the letter’s claims that tribal concerns were ignored, documentation in the court decision shows that the Corps and Dakota Access repeatedly sought to involve the Standing Rock tribe in the planning of the pipeline.

Throughout 2015, the Corps exchanged letters with tribal representatives, looking to arrange an onsite visit to Lake Oahe and to directly address questions and concerns. Throughout August and September, their efforts were stalled by the unwillingness to tribal leaders to meet with them. An October 28 meeting between the Corps and the tribe’s vice chair was cancelled because no one from the tribe was available to attend. When the Standing Rock tribe was invited to a general tribal meeting on December 8-9, 2015, it was not one of the five tribes present.

Only in 2016 did the tribe begin to meet directly with the Corps. By then, the pipeline route had been shifted in several locations where tribal burial sites were discovered. Finally, after more than a year of efforts by the Corps to discuss the project, the Standing Rock tribe decided to sue.

The congressional letter, coming after both a loss in court and a formal directive halting work on the nearly completed project, seems to be the latest attempt to halt a nearly completed project.