In a letter dated Monday, Oct. 19, Mayes’ office said Heap has no legal basis to downgrade or cancel the registrations without affirmative evidence that the voters are not U.S. citizens. The warning comes as Arizona prepares for the Nov. 3 election.

Eighteen of the 24 voters were on the county’s early-voting list, according to the attorney general’s office. One is a military or overseas voter. The office said the 18 should have been mailed ballots earlier in October and that failing to send the overseas voter a ballot 45 days before Election Day violated state law. Friday, Oct. 23, is the final day to mail an early ballot, the letter said.

The case stems from a broader citizenship review. Earlier this year, Heap referred 207 registered voters suspected of not being U.S. citizens to the Maricopa County Attorney’s Office for investigation. County Attorney Rachel Mitchell said in September that of 60 people in the group who had voted in past elections, investigators determined eight were noncitizens. The remaining 52 were citizens, but 24 of them still had an “not eligible” designation, Mayes’ office said.

Mayes’ office said continuing to classify those voters as ineligible could prevent them from casting ballots that are counted. State law, according to the office, requires a recorder who confirms a registrant is not a citizen to cancel the registration and notify the voter, county attorney and attorney general.

The attorney general’s office issued Heap a similar warning in May, saying he lacked authority to mark more than 200 voters ineligible. It said it would sue if he did not restore the 24 registrations. Heap’s office was contacted for comment; no response was included in the information available Wednesday.