(CNN) The Cheyenne River Sioux Tribe has rejected an ultimatum by South Dakota's governor to remove checkpoints on state highways within tribal reservations or risk legal action.
Gov. Kristi Noem sent letters Friday to the leaders of both the Oglala Sioux Tribe and the Cheyenne River Sioux Tribe demanding that checkpoints designed to prevent the spread of coronavirus on tribal land be removed, the governor's office said in a statement.
"We are strongest when we work together; this includes our battle against Covid-19," Noem said. "I request that the tribes immediately cease interfering with or regulating traffic on US and State Highways and remove all travel checkpoints."
In response, Cheyenne River Sioux Tribe Chairman Harold Frazier said in a news release Friday that while he agreed it's important to work together, "you continuing to interfere in our efforts to do what science and facts dictate seriously undermine our ability to protect everyone on the reservation."
"Ignorant statements and fiery rhetoric encourage individuals already under stress from this situation to carry out irrational actions," he said. "We invite you to join us in protecting the lives of our people and those that live on this reservation. I regretfully decline your request."
The purpose of the tribe's actions, Frazier said, is to "save lives rather than save face."
CNN has also reached out to the Oglala Sioux Tribe for comment.
According to Cheyenne River Sioux Tribe checkpoint policies posted on its social media, its reservation residents may travel within South Dakota to areas the state has not deemed a Covid-19 "hotspot" if it's for an essential activity such as medical appointments or to get supplies unavailable on the reservation. But they must complete a health questionnaire when they leave and when they return every time they go through a checkpoint.
South Dakota residents who don't live on the reservation are only allowed there if they're not coming from a hotspot and it is for an essential activity. But they must also complete a health questionnaire.
Those from a South Dakota hotspot or from outside the state cannot come to the reservation unless it is for an essential activity -- but they must obtain a travel permit available on the tribe's website.
Both tribes have also issued strict stay-at-home orders and curfews for their communities. Noem has not issued stay-at-home orders for the state.
Last month, when the checkpoints began, the US Department of the Interior's Bureau of Indian Affairs issued a memorandum saying tribes must consult and come to an agreement with the state of South Dakota before closing or restricting travel on state or US Highways.
There are 169 cases of Covid-19 among Native Americans in the state as of Friday, the health department said. The state has 3,145 confirmed cases and 31 deaths.