North Dakota “has taken steps to worsen” a “confusing and chaotic” situation for Native American voters in the state, alleges a new lawsuit.

The ongoing legal battle over the state’s voter ID law has emerged as a key issue as Sen. Heidi Heitkamp (D) struggles to win re-election in a race that could determine control of the U.S. Senate.

At issue is a provision of the state’s voter ID law that requires the identification to include a residential street address, an obstacle for Native Americans, who often rely on P.O. boxes to receive mail and who may not even have a formal street address assigned to the place where they live.

The street address requirement faced a previous legal challenge, and a district court ruled in favor of the Native Americans bringing the lawsuit by relaxing the requirement so that IDs with a P.O. box or other non-residential addresses would suffice. The decision to water down the requirement was blocked by the appeals court ahead of the 2018 midterms — a move the Supreme Court also backed, letting the state enforce the original version.

The new law was passed by the state’s GOP legislature after Heitkamp, who draws support from tribal voters, eked out a 3,000-vote victory in 2012. She is on the ballot again next week.

The new lawsuit, against Secretary of State Alvin Jaeger, points to the appeals court opinion letting the full requirement go into effect, which signaled that the court would be open to addressing the requirement more narrowly and promised that “if any resident of North Dakota lacks a current residential street address and is denied an opportunity to vote on that basis, the courthouse doors remain open.”

The complaint is brought by Native Americans who have had trouble, for various reasons, obtaining an acceptable ID with a residential street address. The lawsuit also claims that absentee ballot applications have been rejected because the voter’s residential street address was deemed “invalid.”

According to the lawsuit, the problem for Native Americans now is that not only are they being asked to show an ID with a residential address, there is some confusion as to what happens if that address doesn’t match the address in the state’s records.

Election officials’ implementation of the law “has not only required a residential address on a qualifying ID but also required that the residential address match a ‘valid’ address according to the State,” the lawsuit says.

The lawsuit details the many issues the challengers have had in confirming what their “valid” residential address is, given that their communities sometimes don’t use street names, and that government officials appear to be using contradicting systems to determine an individual’s address. It also says that the state has not offered any resources to the Spirit Lake Tribe, one the challengers in the lawsuit, as it attempts to assist its members in obtaining acceptable IDs.

“If the address situation were not confusing and chaotic enough, Defendant Jaeger has taken steps to worsen the situation, refusing to provide public comment on whether poll workers will accept addresses printed on newly issued IDs, while simultaneously issuing statements that residential street addresses on IDs must not be ‘incorrect’—a warning that creates a particular chill for Native American voters, in light of the chaos and uncertainty caused by the rapid response to the newly effective law,” the lawsuit said.

Alvin’s office told TPM that it does “not comment on pending litigation.”

Read the complaint below: