The U.S Supreme Court on Monday agreed to hear a Mississippi case involving the counting of mail-in ballots received after Election Day, a case that could have a ripple effect nationwide. 

The justices agreed to take up an appeal from Mississippi after a panel of three judges appointed by President Donald Trump on the 5th U.S. Circuit Court of Appeals ruled last year that the state law allowing ballots that arrive shortly after Election Day to be counted violated federal law.

Mississippi is among 18 states and the District of Columbia that accept mailed ballots received after Election Day as long as the ballots are postmarked on or before that date, according to the National Conference of State Legislatures.

In this case, the Republican National Committee and the Libertarian Party of Mississippi sued Secretary of State Michael Watson, the official who administers elections. They argued that Congress alone can set a date by which voters must make their choice, not individual states.

Mississippi Attorney General Lynn Fitch’s office is defending Watson in court, arguing that the five-day window after Election Day does not provide additional days for voters to cast a ballot. Rather, it’s simply an extra cushion for election workers to count the ballots. 

“Under federal law, election day is the day for voters to conclusively choose federal officers. Voters make that conclusive choice by casting — marking and submitting — their ballots by election day,” Fitch’s office wrote in court papers. 

The litigation created an unusual scenario where Fitch and Watson, both Republicans, had to fight their own political party in court to defend Mississippi’s law. 

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 law and federal laws. But the New Orleans-based 5th Circuit later reversed him. 

The U.S. Supreme Court has not set a date for oral arguments, but it would likely be argued during the spring. The Court would then likely issue a ruling in the summer of 2026.