Kansas Secretary of State Kris W. Kobach in his Topeka office. (Christopher Smith/For The Washington Post)

A U.S. appeals court panel that barred Kansas, Alabama and Georgia from adding a proof-of-citizenship requirement to a federal voter registration form wrote Monday that federal law leaves it to a federal elections agency — not the states — to determine whether such a change is ­necessary.

The 2-to-1 written opinion follows a Sept. 9 order from the U.S. Court of Appeals for the D.C. ­Circuit.

The panel wrote that although the document requirement “unquestionably” hinders voter registration groups ahead of the November elections, there was “precious little” evidence of voter fraud by noncitizens, the problem the states said the measure is intended to fight.

The Kansas secretary of state had told the court that “between 2003 and 2015 eighteen noncitizens had tried to or successfully registered to vote. Only one of them attempted to use the Federal Form,” the judges wrote.

U.S. Appeals Court Judges Judith W. Rogers and Stephen F. Williams granted a preliminary injunction Sept. 9 that told the states to process the federal voter applications filed since January as if documented proof of citizenship were not required.

Voting rights groups asked for the temporary halt to enforcement as they continued to challenge the document requirement in a case before U.S. District Judge Richard J. Leon.

Monday’s opinion, which noted that voting rights groups probably would win their lawsuit at trial, likely is the final word before the Nov. 8 presidential election but sets up the legal battle over proof-of-citizenship laws for the 2018 federal elections.

“Judge Rogers’s opinion is flawed because it fails to address all of the statutory issues in this case,” as well as a 1994 federal regulation, said Kansas Secretary of State Kris W. Kobach after the ruling on Monday. Kobach pointed to the dissent from U.S. Appeals Court Judge A. Raymond Randolph, who called the court order unconstitutional.

“It is the States, and the States alone, who have the authority and the power to determine the ­eligibility of those who wish to vote in federal elections,” Randolph wrote.

He added, “Neither the Congress nor the President nor any federal commission and, most certainly, not two federal judges sitting in Washington, D.C. (or even eight or nine) have the authority to prevent Kansas, Georgia and Alabama from enforcing their laws in the upcoming federal elections.”

The decision came in a lawsuit by the League of Women Voters and other groups, which sued after what they called an unauthorized and unilateral decision on Jan. 29 by Brian D. Newby, executive director of the U.S. Election Assistance Commission, to grant the three states’ requests to alter the federal registration form to incorporate state identification requirements.

Kansas is the only state enforcing a demand to show documentation such as a birth certificate, passport or naturalization papers to register to vote in federal races, instead of allowing applicants to check a box, sign and swear under penalty of perjury that they are citizens.

In an unusual move, the Justice Department did not defend Newby’s action, siding with voting rights groups and leaving it to outside parties, including Kansas, to intervene in court.

In Monday’s opinion, the appeals court said that Newby acted unilaterally, without a vote by the four-member federal elections panel, and also without determining that the states’ request was necessary to enforce voter-qualification rules.

The groups that sued argued that citizens who lack documents tend to be poor, rural and African American, and the Supreme Court has said the federal form is meant to provide a “backstop” and guarantee a simple way to register to vote in federal elections — no matter what hurdles states impose.

“Permitting the states to dictate the contents of the Federal Form would undermine” its role as a ‘backstop, the two-judge majority wrote. “The Commission, not the states, determines necessity.”

“If the proposed change to the Federal Form is ‘necessary’ to enforce voter qualifications, then the [National Voter Registration Act] and probably the Constitution require its inclusion; if not, the NVRA does not permit its inclusion and the Constitution is silent,” the judges said.