LAS VEGAS (KTNV) — Nevada’s laws allowing the counting of mail-in ballots that arrive up to four days after Election Day — so long as they are postmarked by that date — is constitutional under a Monday ruling from the U.S. Supreme Court.

In a 5-4 ruling, justices upheld a challenge to a Mississippi law that’s similar to Nevada’s statute. Justice Amy Coney Barrett and Chief Justice John Roberts joined with the court’s three liberal members, Sonia Sotomayor, Elena Kagan and Katanji Brown Jackson, to uphold the law.

Conservatives Samuel Alito, Clarence Thomas, Brett Kavanaugh and Neil Gorsuch dissented.

The ruling affects 30 states, all of which allow some ballots received after Election Day to be counted. That includes Nevada, which allows ballots postmarked by Election Day to be received and counted up to four days later, and ballots without a postmark to be received and counted up to three days later.

Plaintiffs in the case — including the Republican National Committee and the Mississippi Republican Party — had contended that federal laws referring to “elections” mean both the casting and counting of ballots, which they said must occur on Election Day.

“The federal election-day statutes do not preempt Mississippi’s law because the defining element of an ‘election’ has always been the electorate’s choice of candidate,” the case summary reads. “And a related federal statute — the Uniformed and Overseas Citizens Absentee Voting Act — confirms that while federal law dictates when ballots must be cast, state law governs when they must be received.”

In Nevada, critics have contended that late-arriving ballots erode confidence in elections, because they delay learning final election results for days and, in some close races, can change the outcome.

Gov. Joe Lombardo has called the weeklong wait for final, unofficial results “a national embarrassment.”

Plaintiffs in the case made similar arguments, but were turned away by the court: “Finally, plaintiffs policy arguments about election integrity and voter confidence are properly addressed to legislatures, not courts,” the case summary reads.

Several attempts to require ballots to be received by Election Day have been introduced in Nevada’s Legislature, but none have been successful in the Democratically controlled body.

Secretary of State Cisco Aguilar has argued that the overwhelming majority of ballots are in and counted by Election Day, and only the closest races may be changed by late-arriving ballots. He’s advocated for more resources for county clerks and voter registrars to be able to count mail ballots more quickly.

Under the ruling, nothing will change for Nevada voters going to the polls in four months to vote in the November election. But officials still encourage voters to send in their mail ballots early, or to put them in drop boxes at voting centers during early voting or on Election Day.

Supreme Court upholds late-arriving mail ballots in Mississippi