The U.S. Supreme Court on Monday upheld a Mississippi law in a ruling that will allow more than a dozen states to count mail-in ballots that arrive after Election Day. This deals a blow to President Donald Trump’s efforts to federalize state elections and limit mail-in ballot counting. 

The nation’s highest court ruled 5-4 in favor of Mississippi Secretary of State Michael Watson, who was forced to defend the lawsuit as the administrator of the state’s elections. The state Legislature enacted a law in 2020 during the COVID-19 pandemic to give voters a grace period for mailing their ballots. 

Justice Amy Coney Barrett, writing for the majority, said federal law only requires voters to cast their ballots by Election Day, but it does not require election officials to receive the ballots by that date.

“In sum, the election-day statutes require the electorate’s choice to be made on election day,” Barrett wrote. “That occurs so long as election day is the deadline for individuals to vote — as it is in Mississippi.”

READ MORE: U.S. Supreme Court agrees to hear Mississippi mail-in ballots case

In 2024, the Mississippi Republican Party, the Republican National Committee, a Mississippi voter and a county election official filed the federal lawsuit challenging the five-day window. The state Libertarian Party filed a similar lawsuit a few weeks later, which was combined with the first. 

The parties argued that the state law conflicted with the federal law setting the Tuesday after the first Monday in November as the “election day.”

U.S. District Judge Louis Guirola Jr., a George W. Bush-appointed judge, initially ruled last year in Gulfport that there was no conflict between the state and federal laws. But a three-judge panel of the New Orleans-based 5th Circuit Court of Appeals later reversed him, and the full court declined to rehear the case.

Republican Attorney General Lynn Fitch’s office defended the state in court and told Mississippi Today in a statement that, since the Supreme Court affirmed the principle of federalism, she is hopeful that the Mississippi Legislature will now amend the state law that prompted the litigation and “require absentee ballots be received on the same day ballots are cast at the polling place.”

“President Trump is right to prioritize improving public trust in our elections,” Fitch said.

Fitch was defending the position of Republican Watson against the national Republican Party. In a statement, Watson said the ruling confirms that laws regulating voting are to be made by Congress or, in its absence, state legislatures.

“While I oppose the practice of counting ballots received after Election Day, the principle of federalism is a core tenet of my conservatism,” Watson said. “I deeply value the rights of states to govern themselves, including the administration of elections, so long as they do not conflict with federal law.”

Republican Gov. Tate Reeves also called on the Legislature to change the law during the next legislative session and said he disagrees with the court’s decision.

“But just because the Court ruled the practice constitutional, doesn’t mean we should allow it in our state,” Reeves said.

Jade Craig, an assistant professor of law at the University of Mississippi, called the court’s decision “a win for states’ rights and democracy in terms of states having the authority to set their own voting parameters.”

“It is a real relief and a great achievement for Mississippi and all the states that have similar laws that provide for mail-in voting,” Craig said.

Craig said it was a surprise that a Mississippi voting law was challenged, seemingly setting up an intraparty conflict between Republican state officials and the national party. But the decision establishes that both red and blue states have “a shared set of problems that the Court is responsible for addressing in ways that are equitable across the country,” Craig said.

Bradley Heard, deputy legal director for the Southern Poverty Law Center, said “common sense prevailed today.”

“When a voter mails a ballot postmarked by Election Day and it arrives within the allotted window of time, they have done what the law requires — laws which have been on the books since as early as the Civil War. Votes cast by mail are valid votes, and all valid votes should be counted,” Heard said.

In an emailed statement, Republican National Committee Chairman Joe Gruters accused Democrats of “inviting chaos at the ballot box” and urged Congress to pass the Safeguard American Voter Eligibility, or SAVE America Act, a Trump-backed proposal that Republicans say will improve election integrity.

“Republicans are not going to be deterred by this decision, and the RNC will keep fighting to have elections end on Election Day as Americans want,” Gruters said.