Approaching the Standing Rock Reservation to stand with the Water Protectors, you couldn’t miss the dramatic display of tribal flags flying high along the dirt driveway and surrounding the perimeter of the large campgrounds. Scattered between hundreds of flags are banners bearing messages such as: Mni Wiconi, “water is life” in the Lakota language.

Also scattered among the flags were banners calling for the release of Leonard Peltier, a Native American who has been in jail for more than 41 years, unjustly convicted of the 1975 murders of FBI special agents Jack Coler and Ronald Williams on the Pine Ridge Reservation in South Dakota. Barack Obama just pardoned or commuted the sentence of 231 individuals on Monday, and Peltier was not among them.

We represent Leonard Peltier in his 2016 clemency petition, which asks Obama to allow him to live his final years at home on the Turtle Mountain Reservation in North Dakota. Mr Peltier is old, ill and a threat to no one. The petition seeks his release in the interests of justice and reconciliation and is supported by Nobel Peace Prize laureates, humanitarians and scholars. Rights groups have embraced his cause, including more than 100,000 people who have signed an Amnesty International petition calling for his release.

Over the course of our legal representation, we reviewed old government records obtained through decades of litigation under the Freedom of Information Act as well as court proceedings. Viewed through today’s lens, the case presents a glimpse of an era when social activists were considered a threat and Native American activists, in particular, were branded “extremists”.

The incident took place in the wake of the American Indian Movement’s (Aim’s) 1973 siege of the Wounded Knee Massacre site, where hundreds of unarmed Lakota men, women and children were murdered by the US Army in 1890. That siege brought attention to broken treaties, failed promises and tribal corruption. Under the FBI’s exclusive jurisdiction for the prosecution of major crimes, violence escalated in the impoverished and politically charged community; it is an era that locals refer to as the “Reign of Terror”.

Leonard Peltier arrived in June 1975 to help protect Oglala Lakota families from violence. On 26 June that year, two FBI agents entered the private property in unmarked cars and gunfire erupted. By the end of the incident, Agents Coler and Williams died, as did Native American Joseph Stuntz, although no charges were brought against anyone for his death.

Peltier states in the petition: “I did not wake up ... planning to injure or shoot federal agents, and did not gain anything from participating in the incident … I was [on Pine Ridge Reservation] to protect ... residents, not to cause harm … If I could have prevented this tragedy from occurring, I would have done so.”

FBI agents from across the country immediately were dispatched to Pine Ridge Reservation, where they launched what amounted to an assault upon the Oglala Lakota Nation. They made warrantless searches of homes, offices and residences, coerced testimony, detained people without cause and even restrained an attorney who attempted to prevent a warrantless search. Requests at the time from US Civil Rights Commission Investigator William Muldrow for independent oversight of the FBI were ignored by federal officials.

The injustices that contributed to Peltier’s conviction are not subject to credible dispute. Federal agents made false statements to the press; submitted false affidavits to courts; coerced alleged witness statements; and deliberately withheld critical ballistics reports in order to gain an unfair advantage at trial.

When the ballistics results were discovered after trial, the government’s attorneys conceded – as they had to – that they had no credible evidence regarding who shot the FBI agents, and did not know whose weapon actually killed the agents.

Peltier’s many requests for a new trial were opposed by the government and denied by the courts. He remains in jail today primarily because of an “accomplice” theory of liability which was included in the written charges but not argued to the jury, that he allegedly assisted someone in an unidentified way.

The clemency petition does not reargue the verdict, but rather, it sets forth the facts and is supported by the FBI’s own records. If Obama does not grant the petition before he leaves office in just a few weeks, then it will be a death sentence for Peltier, who is next eligible for parole in 2024.

The tragic loss of all three lives will never be forgotten. That pain should not blind us, however, to what the case represented at the time, and has come to represent since.

In our opinion, history will record Peltier’s case as one of the greatest injustices in the history of the American justice system.

When a nation fails to reckon with its past, it risks the perpetuation of intolerance on one hand, and resentment on the other. To “seize a better future” as Obama has said, our nation must reckon with its historical injustices against Native Americans.

Granting clemency to Leonard Peltier is not a referendum on federal law enforcement. It is a declaration to the world that we embrace Native Americans as equal members of society, and a pledge to become a stronger and fairer nation. It presents a moral imperative relevant to our nation’s past, present and future – and to Obama’s legacy.

After 41 years, please Mr President, free Leonard Peltier.