PHOENIX - The U.S. Supreme Court will consider how far Arizona - and other states - can go in requiring voters to prove citizenship when registering.

In a brief order, the justices agreed to review a ruling by the 9th U.S. Circuit Court of Appeals that said Arizona cannot refuse to register voters who do not provide proof of citizenship if they fill out a special registration form prepared by the federal Election Assistance Commission. That form requires only that the person avows, under oath and penalty of perjury, that he or she is eligible to vote.

In its June ruling, the appellate court said Arizona's proof-of-citizenship requirement, approved by voters in 2004, directly conflicts with federal law.

In asking the high court to overturn that ruling, Arizona Attorney General Tom Horne wrote, "Although the applicant is required to sign a statement under oath that he is a citizen, someone willing to commit voter fraud will be willing to sign that statement. Only by requiring evidence of citizenship can the state screen out noncitizens who are attempting to vote."

But Nina Perales of the Mexican American Legal Defense and Educational Fund, countered, "It is an unconstitutional burden to require voters who are using the federal form to supply more information than is required by the federal government."

The justices plan to hear arguments in February.

The fight involves a 2004 voter-approved measure that requires both proof of citizenship to register and identification to cast a ballot at the polls.

Foes challenged both.

The courts sided with the state on the ID at polling places requirement. While that remains a legal issue in some states, foes of the Arizona law never appealed that decision and it will not be an issue when the Supreme Court looks at the law next year.

In concluding Arizona's citizenship-proof requirements cannot override federal law appeals, Judge Sandra Ikuta pointed out Congress, through the National Voting Rights Act, mandated creation of a single specific form designed to allow individuals to register to vote by mail. And federal lawmakers empowered the Election Assistance Commission to design the form and decide what is necessary.

That commission, she noted, chose not to include a proof-of-citizenship requirement.

What that means, the judge said, is Arizona election officials cannot refuse to register those people who sign up using that federal form, even if they do not provide the state-mandated identification.

Arizona has remained free, however, to continue to demand proof of citizenship from those who go to state offices and register using a state-provided form.

Both sides agree only a small percentage of people use the federal form.

Maricopa County Elections Director Karen Osborne said she has registered fewer than 3,000 people using the federal form since the 9th Circuit ruling. By comparison, there are close to 2 million people registered in the county.

Horne, in his bid to persuade the Supreme Court to uphold the state law, is arguing nothing in the 2004 ballot measure conflicts with the National Voting Rights Act.

"Because only U.S. citizens are eligible to vote, Proposition 200's evidence-of-citizenship requirement is consistent with the NVRA's express goals," Horne is arguing to the high court. "Congress did not intend the NVRA to bar states from properly assessing whether an applicant who registers to vote is eligible to vote."

Horne said the Arizona law does not interfere with the federal law "because requiring evidence of citizenship imposes a minimal burden on a limited number of persons and further the federal government's and the states' broad interest in protecting election integrity."

The appeals court rejected a similar argument in June.

But Horne wrote he is seeking to reverse that decision because without proof, "Arizona is forced to accept what amounts to an honor system as to whether applicants are citizens or not."

Perales responded, "There is no evidence that any voter has ever used the federal form to register as a noncitizen."

Secretary of State Ken Bennett acknowledged he has no evidence people who are not citizens are registering to vote, either now with the federal form or before the 2004 proof-of-citizenship requirement, since there was no way to determine if those who are not citizens were going to the polls, as there was no verification process.

"Arizona is forced to accept what amounts to an honor system as to whether applicants are citizens or not."

Tom Horne,

Arizona attorney general