Kristi Noem appealed to the Trump administration for help Wednesday in resolving a dispute over roadside checkpoints set up by two Native American tribes trying to curb the spread of the coronavirus, the latest move in a clash over which government entity has the ultimate legal authority.

Noem, a Republican who assumed office last year, wrote in a letter to President Donald Trump that the issue is "not a matter of tribal sovereignty" because South Dakota has rights allowing residents and travelers to access the roadways, and that the federal government has "an interest in interstate commerce." She also argued that the checkpoints do little to stop the coronavirus from spreading, and if anything, they increase the risk of transmission because people are exposing themselves when they're forced to stop.

Noem, who has previously threatened legal action against the Cheyenne River Sioux and the Oglala Sioux tribes, wrote that as an alternative to litigation, she'd like for federal assistance in shutting down the "unlawful" checkpoints and requiring the Cheyenne River Sioux, specifically, to comply with a Bureau of Indian Affairs memo on the matter.

Noem had warned the tribes to take down the checkpoints on state and federal highways within 48 hours or face court action.

Harold Frazier, the chairman of the Cheyenne River Sioux Tribe, said on MSNBC last week in response to Noem's ultimatum that "we have every legal right to do what we're doing" and that such a precautionary measure is warranted because the tribe has insufficient medical resources to combat COVID-19, the disease caused by the coronavirus.

A third tribe in South Dakota, the Rosebud Sioux, said in a Facebook post Monday that it has also set up driver checkpoints, although "commercial traffic will be allowed to proceed through the checkpoints on to their destinations without issue." Noem has not mentioned the tribe in her public comments.

She had sought to come up with a compromise with tribes allowing for checkpoints on tribal roads, but not state and federal ones.

In a letter to Noem last week, Frazier said the tribe would consider her request — but now her bid for White House involvement has thrown the tribes for a loop.

This case, no matter how it progresses, he said, represents the complexities associated with tribal rights and culture and how the federal government has "tried to shoehorn" tribes into an Anglo American system of justice and authority