The Supreme Court on Thursday allowed Arizona officials to enforce part of a state election law from 2022 that requires proof of citizenship when using a state form to register to vote.

But in a brief order Thursday, the justices also blocked for now another part of the law that sought to prevent voters from casting ballots in the presidential election without proof of citizenship.

The order comes after an emergency application from the Republican National Committee and state officials who sought to uphold the Arizona law. The court voted 5-4 on the split outcome but did not explain their reasoning.

Justices Clarence Thomas, Samuel A. Alito Jr., and Neil M. Gorsuch noted they would have allowed the state to enforce the entire law. And Justices Sonia Sotomayor, Elena Kagan, Amy Coney Barrett and Ketanji Brown Jackson noted they would have kept the law paused.

The state law requires anyone registering to vote in the state, whether by using a state-issued form or the federal one, to provide proof of citizenship or have their registration rejected. Additionally, a separate provision prevented anyone who did not provide proof of citizenship from voting in the presidential election.

Civil rights groups and the Biden administration challenged the law, arguing it conflicts with federal voter registration law and a 2018 settlement governing voter registration. And earlier this year, a federal judge ruled the state could not enforce certain provisions of the state law.

The RNC and Republican leaders of the state legislature appealed that injunction to the U.S. Court of Appeals for the 9th Circuit. Initially, a three-judge panel of that court allowed state officials to enforce the law. But another group of 9th Circuit judges voted 2-1 last month to keep it on hold while the RNC appeal played out.

The RNC and the Republican leaders then asked the Supreme Court to intervene and let the state enforce the law during the court fight. They argued the state should be able to set its own rules for voter registration and that the courts should not throw out election rules at the last minute.

“The district court’s injunction is an unprecedented abrogation of the Arizona Legislature’s sovereign authority to determine the qualifications of voters and structure participation in its elections,” the RNC wrote in its application to the Supreme Court.

The Biden administration argued in a court filing that the statute should remain paused, and that “judicial intervention at this stage would undermine the orderly administration of the election, risking the disfranchisement of thousands of voters who have already registered to vote using the federal form.”

Attorneys for the civil rights groups and national and state Democrats argued that Arizona does not have the authority to change federal voter registration rules, which are governed by the National Voter Registration Act, and require states accept the form issued by the federal government.

Additionally, the groups said state officials entered into a settlement agreement in 2018 with civil rights groups to have the state treat state and federal voter registration the same way.

Arizona Secretary of State Adrian Fontes, a Democrat, also argued against the enforcement of the law. The law’s provisions on registration require enforcement by local county officials rather than by Fontes’ office.

Fontes argued in a court filing that allowing the law to go into effect now would “create chaos and confusion and in turn undermine the credibility of our elections.” Fontes noted that a Supreme Court ruling to allow enforcement of the law would change the rules for voter registration less than two months before the deadline.

Proof of citizenship for voters has become a major election issue, buoyed by evidence-free claims by President Donald Trump and other Republican officials that noncitizens vote in substantial numbers in federal elections.

Earlier this year, the House passed a measure that would require similar proof of citizenship for voter registration nationwide. Voting as a noncitizen is already a federal crime.