The US Supreme Court on Monday ruled that federal law does not bar states from counting absentee ballots that arrive after election day, so long as they are postmarked by that date.

The 5-4 decision in Watson v. Republican National Committee reversed a US Court of Appeals for the Fifth Circuit ruling that had struck down a Mississippi law allowing officials to count absentee ballots received up to five business days after election day, provided they are postmarked on or before that date. Justice Amy Coney Barrett wrote for the majority in an unusual alignment that bridged the Court’s ideological divide, joined by Chief Justice John Roberts and the Court’s three liberal justices—Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson.

At issue were the three federal statutes (2 U.S.C. § 7, 2 U.S.C. § 1, and 3 U.S.C. § 1) which set a single Tuesday in November for the “election” of the president, senators and representatives. The Republican National Committee, the Mississippi Republican Party, and the Libertarian Party of Mississippi had argued that the word “election” sets a deadline for both casting and receiving ballots, meaning federal law required all ballots to be in hand by election day.

The Court disagreed. Barrett wrote that the defining element of an “election” has always been the electorate’s choice of candidate, which is complete when voting ends, not when ballots are received. The majority pointed to the Uniformed and Overseas Citizens Absentee Voting Act (UOCAVA), which it said repeatedly presupposes that ballot-receipt deadlines are a matter of state law, and to the Constitution’s electoral college provisions, which fix a uniform day for casting votes but say nothing about receipt.

The Court framed the question narrowly, declining to address the scope of Congress’s authority to regulate federal elections or a late-raised argument that ballots recallable from the mail are never truly “cast” by election day.

Justice Samuel Alito dissented, joined by Justices Clarence Thomas and Neil Gorsuch, and by Justice Brett Kavanaugh in part. Alito argued that the electorate’s collective choice is not authoritatively expressed until ballots are collected, and warned the ruling leaves open questions about who can deliver ballots and how late they can arrive, while heightening the risk of fraud and post-election-day result reversals that can erode public confidence.

The case will return to the Fifth Circuit for further proceedings.