Mail ballots.

The issue that just won’t go away.

Hard to believe that this one does not involve Pennsylvania.

The United States Supreme Court on Monday agreed to hear a case that will set the stage for a major ruling on election law – does federal law require ballots to not only be cast by voters but also be received by election officials by Election Day.

The high court granted certiorari to review Watson v. Republican National Committee, a challenge by the RNC and others to a Mississippi law that allows mail-in ballots to be counted as long as they are received within five business days after Election Day.

Pennsylvania law requires mail ballots to be received at county election offices by the close of polls (8 p.m. ET) on Election Day with exceptions for military and overseas voters.

A federal judge in Mississippi upheld the state’s law in 2024, rejecting the challengers’ contention that it conflicted with federal law.

Senior U.S. District Judge Louis Guirola explained that, according to Supreme Court precedent, “Congress set a national election day to avoid the ‘evils’ of burdening citizens with multiple election days and of risking undue influence upon voters in one state from the announced tallies in states voting earlier. Neither of those concerns,” he concluded, “is raised by allowing a reasonable interval for ballots cast and postmarked by election day to arrive by mail.”

The U.S. Court of Appeals for the 5th Circuit reversed the decision, ruling that federal election law, which sets the Tuesday after the first Monday in November as the “election” day for federal offices, requires all ballots to be received by that day. The full 5th Circuit declined to rehear the case, over a dissent by five judges.

Mississippi appealed to the Supreme Court in June, arguing “an ‘election’ is the conclusive choice of an officer” – which occurs by the deadline as long as voters cast their ballots by then, even if election officials do not receive them by that day. With the 2026 elections looming, “[s]tates need to know whether federal law permits post-election-day ballot-receipt laws—and thus whether they must change their laws to comply with federal law or whether they may change their laws on policy grounds.” Moreover, the state added, “[t]he stakes are high: ballots cast by—but received after—election day can swing close races and change the course of the country.”

A group of 19 states, including California, Maryland, New Jersey, New York, and the District of Columbia filed a “friend of the court” brief supporting Mississippi. They called the 5th Circuit’s ruling “both wrong and destabilizing,” adding that “last-minute election-related limbo is the last thing states and courts need.” In particular, they noted, “the Fifth Circuit’s rule jeopardizes the ability of states to count lawfully cast ballots from military service members and their families who are stationed abroad.” 

In a brief unsigned order on Monday morning, the justices agreed to take up the case. The court will likely hear oral arguments sometime next year, with a decision to follow by late June or early July.