The Standing Rock Sioux Tribe Chairman Dave Archambault II penned a letter to President Donald Trump yesterday (January 25) in which he urged the president to meet with him and his tribe to discuss the Dakota Access Pipeline.

The chairman also asked Trump to allow for an Environmental Impact Statement (EIS), which Trump called on the Army Corps of Engineers to consider withdrawing in a January 24 presidential memorandum that seeks to complete construction on the 1,172-mile pipeline.

In his letter, Archambault reminds the president of the details regarding the EIS, a lengthy process that involves a public comment period, which is now open, and a discussion of alternatives to the project since an EIS is typically launched after an agency finds that said project would impact the surrounding environment significantly.

This wasn’t, however, the case with the Dakota Access Pipeline. The EIS was established through an Army Corps of Engineers memo on December 4 after it denied an easement for the pipeline to cross Lake Oahe on the Missouri River—an peculiar approach to the process.

The chairman writes:

President Trump, the EIS is already underway. The comment period does not close until February 20th and the Department of the Army has already received tens of thousands of comments. This change in course is arbitrary and without justification; the law requires that changes in agency positions be backed by new circumstances or new evidence, not simply by the President’s whim. It makes it even more difficult when one considers the close personal ties you and your associates have had with Energy Transfer Partners and Sunoco.

The letter goes further in calling the presidential memo a “disregard [for] tribal interests.” Read the letter in full here.