BISMARCK, N.D. (AP) – Seven citizens of the Turtle Mountain Band of Chippewa are suing North Dakota’s chief elections officer, alleging the state’s voter identification requirements are unconstitutional and “disproportionately burden and disenfranchise Native Americans.”

The federal lawsuit filed Wednesday against Secretary of State Al Jaeger alleges that North Dakota’s voter ID requirements violate the U.S. Voting Rights Act. The suit argues that some tribal members can’t afford the required identification, and others had to pay to get their tribal IDs updated with a valid address, forcing them to “pay to vote.”

The Turtle Mountain reservation, in north-central North Dakota, receives one-quarter of all welfare payments in the state, according to tribal officials.

The 45-page complaint is backed by the Colorado-based Native American Rights Fund, along with Bismarck attorney Tom Dickson. The lawsuit seeks to halt enforcement of the state’s voter identification requirements and asks for unspecified attorney fees and costs.

Jaeger said he was served with the lawsuit Thursday but could not immediately comment on it.

“We have to review it,” he said.

North Dakota is the only state without voter registration, but state law has required voters to provide ID since 2004. Prior to that, casting one’s ballot was an informal process in most precincts, and identification cards were seldom requested.

North Dakota now requires a driver’s license as identification or identity cards issued by the state, long-term care facilities or North Dakota’s American Indian tribes. All must have a valid address.

Prior to 2013, if a voter lacked an ID card but a poll worker had firsthand knowledge of the person’s identity and residence, the voter was allowed to cast a ballot. The voter also could sign an affidavit attesting to his or her eligibility to vote in the precinct.

Matthew Campbell, a Native American Rights Fund attorney, said those were “fail-safe provisions for indigent voters or someone who got their wallet stolen on the way to the polls.”

“Everyone who is qualified should be entitled to vote,” he said. “The way the system was seemed to work fine.”

North Dakota launched a public education campaign two years ago aimed at reminding people to bring proper identification to the polls to prove they are eligible to vote. The advertising campaign was funded with a $700,000 federal grant as part of the Help America Vote Act.

Jaeger said his office has worked with several groups, including all American Indian groups in North Dakota, to ensure that all eligible voters are able to exercise their right to vote, including emphasizing the need for valid addresses on required identification.

“A post office box does not establish residency,” he said.