The U.S. Supreme Court on Thursday rejected a Republican push that could have blocked more than 41,000 Arizona voters from casting ballots for president in the state that President Joe Biden, a Democrat, won by fewer than 11,000 votes four years ago.

But in a 5-4 order, the court allowed some enforcement of regulations barring people from voting if they don’t provide proof of citizenship when they register.

The justices acted on an emergency appeal filed by state and national Republicans that sought to give full effect to voting measures enacted in 2022 following Biden’s narrow win over Republican Donald Trump.

The court did not detail its reasoning in a brief order. Conservative Justices Clarence Thomas, Samuel Alito and Neil Gorsuch would have allowed the law to be fully enforced, while Justice Amy Coney Barrett would have joined with the court’s three liberals in fully rejecting the push, the order states.

The legal fight will continue in lower courts.

The court’s action came after a lower court blocked a requirement that called for state voter registration forms to be rejected if they are not accompanied by documents proving U.S. citizenship. A second measure, also not in effect, would have prohibited voting in presidential elections or by mail if registrants don’t prove they are U.S. citizens. Federal law requires voters to swear they are U.S. citizens under penalty of perjury but does not require proof of citizenship either to vote in federal elections in person or cast ballots by mail.

The measures were passed on party-line votes and signed into law by then-Gov. Doug Ducey, a Republican, amid a wave of proposals that Republicans introduced around the country after Biden’s 2020 victory over Trump, including in Arizona.

For state and local elections, voters must provide proof of citizenship when they register or have it on file with the state. Since that isn’t a requirement for federal elections for Congress or president, tens of thousands of voters who haven’t provided proof of citizenship are registered only for federal elections.

There were 41,352 of those voters registered as of August 9 in Arizona, said Secretary of State Adrian Fontes, a Democrat.

Fontes warned in a court filing that an order in favor of the state and national Republicans this close to the November election “will create chaos and confusion.”

The voters most affected would include military service members, students and Native Americans, Fontes said. About 27% of those voters are registered Democrats and 15% are Republicans. More than half, 54%, are registered independents, according to state data.

Voting rights groups and the Biden administration had sued over the Arizona laws.

Federal-only voters have been a subject of political wrangling since the Supreme Court ruled in 2013 that Arizona cannot require documentary proof of citizenship for people to vote in national elections. The state responded by creating two classes of voters: those who can vote in all races and those who can vote only in federal elections.

One of the new laws sought to further divide voters, allowing votes in congressional elections without proof of citizenship, but denying the vote in presidential contests.

The 2022 law has drawn fierce opposition from voting rights advocates, who described the statute as an attempt to get the issue back in front of the now more-conservative Supreme Court.

Proponents say the measure is about eliminating opportunities for fraud. There is no evidence that the existence of federal-only voters has allowed noncitizens to illegally vote, but Republicans have nonetheless worked aggressively to restrict federal-only voting.

The Legislature’s own lawyers had said much of the measure was unconstitutional, directly contradicted the earlier Supreme Court decision and was likely to be thrown out in court.