"The Cheyenne River Sioux Tribe in South Dakota is refusing to end coronavirus checkpoints declared illegal by the state's governor, saying they are the best tool they have to stop the virus from spreading," CNN reports. "Gov. Kristi Noem sent letters Friday to the leaders of the Oglala Sioux and the Cheyenne River Sioux tribes demanding that the checkpoints along the U.S. and state highways through tribal land be removed."

Noem said the checkpoints are not legal because they're on state highways and have hindered travel and essential services from being delivered; she threatened to sue the tribes in federal court if they don't comply, Vanessa Romo reports for NPR.

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

Leaders for both tribes say the checkpoints are necessary to protect their people, and have also issued lockdowns, stay-at-home-orders and curfews. Noem has not taken such measures statewide, Romo reports.

Many tribes have been hard-hit by the pandemic, often because of poor infrastructure, underlying health conditions, and limited access to health care.