Concerned and angered by the use of dogs, pepper spray, military tactics and strip searches against unarmed water protectors at the construction sites of the Dakota Access oil pipeline, Standing Rock Sioux Chairman David Archambault II is asking the U.S. Department of Justice to step in.

“I am seeking a Justice Department investigation because I am concerned about the safety of the people,” Archambault said in a statement. “Too often these kinds of investigations take place only after some use of excessive force by the police creates a tragedy. I hope and pray that the Department will see the wisdom of acting now to prevent such an outcome.”

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In a formal letter, Archambault called on U.S. Attorney General Loretta Lynch to investigate the alleged civil rights violations, outlining the ways in which the protectors’ safety is being compromised and their First Amendment rights jeopardized.

“We have seen local law enforcement fail to protect our people, as private security for Dakota Access used dogs and pepper spray to attack Indian people opposed to the pipeline,” Archambault said in an October 24 letter to Lynch. “And local law enforcement allowed this to happen.”

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Archambault said protesters and tribal members have told him that “the militarization of law enforcement agencies has escalated violence at the campsite,” even as the tribe’s lawful efforts to keep the 1,172-mile-long pipeline from being routed through sacred burial sites and underneath the Missouri River a half mile from its reservation have drawn worldwide support.

“Firsthand accounts and videos filmed by participants reveal a pattern of strong-arm tactics targeting Native Americans and peaceful protestors,” the Standing Rock Sioux said in the statement. “The abuses include strip searches, violent security dog attacks, pepper-spraying of youth and intimidation by law enforcement.”

Archambault’s letter went further, describing roadblocks, checkpoints and unwarranted stops, all of which “are clearly targeted at Indian people, and are designed to intimidate free speech.”

Add to that the “constant surveillance, with low-flying planes and helicopters constantly overhead at the camps of the water protectors,” the confiscation of at least one drone and the shooting down of another, even those being used by journalists, plus the actual arrests of journalists such as Democracy Now!’s Amy Goodman, add up to a “larger effort by local law enforcement to intimidate the press and to prevent the full and fair reporting of the activities of law enforcement on this matter,” Archambault’s letter said.

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“Rather than seeking to keep the peace, law enforcement personnel are clearly working in tandem with private security of Dakota Access,” the chairman wrote, adding that the tactics not only evoke the civil rights movement of 50 years ago but also bring up the collective memory of the U.S. government’s “long and sad history of using military force against indigenous people.”