South Dakota Gov. Kristi Noem says she will follow through on her threat to take legal action against two Native American tribes that have defied orders to remove highway checkpoints onto tribal land in an effort to prevent the spread of the coronavirus on their reservations.

In a Monday press conference, Noem affirmed that her office will take the Cheyenne River Sioux Tribe and Oglala Sioux Tribe to federal court, saying the checkpoints that were put in place last month on state and federal highways have prevented essential services from making their way to areas in need.

"We do have people that have been going to these areas that have been involved in essential services that have not been allowed to go forward. We have people who live in tribal areas, and also have property there such as cattle or ranches, and they're not allowed to go there and check on their property or to do normal day-to-day business," she said.

In letters to the Cheyenne River Sioux Tribe and the Oglala Sioux Tribe last Friday, the Republican governor said the state would take legal action if the tribes did not remove the checkpoints within 48 hours. As of Monday night it was unclear whether the state had filed court papers.

The restrictions require residents and nonresidents to fill out a health questionnaire each time they enter or leave tribal lands. They also limit nonresidents from entering the reservations unless on essential business or if the tribal government has granted them a travel permit. However, those who wish to drive straight through are allowed to pass, according to the tribes.

Noem said her office has been told of instances where through-travelers have been prevented from entering the reservations.

"We do have situations where people have tried to just travel through, not stop, and have been turned around," Noem said. "We do have people that have been going to these areas that have been involved in essential services that have not been allowed to go forward."

The governor added that it is her office's responsibility to facilitate access through each reservation — a spread of more than 15,000 square miles combined.

Meanwhile, the governments of both tribes say the decision to create an "island of safety" by restricting nonessential travel is well within their rights.

"We have every legal right to do what we're doing," Cheyenne River Sioux Tribe Chairman Harold Frazier told MSNBC on Sunday.

Both tribes have issued lockdowns, stay-at-home orders and curfews, while Noem has refrained from enacting such measures across the state.

Frazier and Oglala Sioux Tribe President Julian Bear Runner contend that the tribal measures were put in place out of concern that an outbreak could overwhelm their limited health care facilities.

"When we talk about rights, one of the greatest rights is the right to live," Frazier said on MSNBC. "And that's all we're trying to do is to provide that right for our residents of this reservation."

On Sunday, a bipartisan group of South Dakota legislators whose districts include tribal lands said in a letter to Noem, "Your statement that Tribal governments do not possess the ability to establish checkpoints within the boundaries of their homelands is not accurate."

They said that the Fort Laramie Treaties of 1851 and 1868 gave tribes such powers. The legislators also said a 1990 opinion by the 8th Circuit Court of Appeals said the state has no jurisdiction over highways running through Native American land without tribal consent.

"We do not wish to be party of another lawsuit that will ultimately cost the people of South Dakota more money," the legislators said.

Noem said she is working with the lawmakers to find a resolution to the issue but insisted state and federal highways are not under tribal control.

A federal court will provide needed "clarity," she said.

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