(CNN)More than 150 years ago, leaders in Colorado issued proclamations urging citizens to kill Native Americans in the area. That order was never officially rescinded -- until now.
On Tuesday, Colorado Gov. Jared Polis signed an executive order rescinding the proclamation, ordered by Territorial Gov. John Evans in 1864.
"The 1864 Proclamations were never lawful because they violated established treaty rights and federal Indian law. Further, when Colorado became a state, they never became law, as they were superseded by the Colorado Constitution, United States Constitution, and Colorado criminal code," the executive order reads.
The proclamations issued by then-Gov. Evans warned that "all hostile Indians would be pursued and destroyed" unless they left their homes and gathered at certain camps. It authorized citizens of the territory to "kill and destroy ... hostile Indians" and steal the Natives' land and property, according to the executive order.
Gov. Evans also supplied organized militias with arms and ammunition, according to the Sand Creek Massacre Foundation.
The 1864 proclamations led to the Sand Creek Massacre later that year, where troops killed hundreds of Cheyenne and Arapahoe people. In 2014, then-Gov. John Hickenlooper formally apologized to the descendents of the victims of the massacre.
Because the proclamations were never officially rescinded, "they therefore remain as a symbol of a gross abuse of executive power during that grave period in our State's history," the executive order signed this week reads.
"When then-Gov. Evans made that proclamation, he said that you can hunt Native people, just as if you could hunt a buffalo, an antelope, an elk, a deer. It was open season," said Reggie Wassana, governor of the Cheyenne and Arapaho Tribes, at Tuesday's ceremony. "And we do appreciate what Gov. Polis has acknowledged. He wants to try to make a wrong right. And that's what we're here for today and that's what we look forward to, is that we would like to see all those wrongs that were done all those years ago come back to right."
Tribal leaders and members from the Southern Ute, Ute Mountain Ute, Cheyenne and Arapaho, and the Northern Arapaho tribes also attended the ceremony, according to CNN affiliate KRDO.
The move by Polis is among one of many recent gestures that aim to at least symbolically repair the harm done to Native populations in the US.
Multiple sports teams in the US have made moves to remove stereotypical, offensive or appropriative portrayals of Native Americans, and Interior Secretary Deb Haaland announced a new unit earlier this year within the Bureau of Indian Affairs to tackle the decades-long crisis of missing and murdered Natives.
Meanwhile, movements to reclaim Native land have also steadily gained momentum.