The United States Supreme Court has ruled that states can continue to count ballots that arrive after election day as long as they are postmarked on the date of the poll, landing a major blow to President Donald Trump’s administration’s attempt to crack down on mail-in ballots. 

In a 5-4 majority decision on Monday, the apex court rejected the lawsuit filed by the Republican National Congress, challenging a Mississippi state law that allows mail-in ballots to be counted if they arrive within five business days of the election. 

More than a dozen other American states, including Washington, D.C., and three U.S. territories, have similar laws. 

“Nothing in the federal election-day statutes requires ballots to be received by election day,” conservative Justice Amy Coney Barrett, who joined Chief Justice John Roberts and the three liberal justices, Sonya Sotomayor, Elena Kagan and Ketanji Brown Jackson, wrote in the majority opinion. 

Meanwhile, Samuel Alito, Clarence Thomas, Neil Gorsuch and John Kavanaugh were the dissenting justices. 

Mr Trump and his supporters have regularly voiced their opposition against mail-in ballots, which millions of Americans rely on to cast their votes, alleging the process is being exploited by the opposition to commit electoral fraud. 

However, the president does not have the power to end it himself, as election processes in the United States are managed under local and state laws and policies rather than federal regulations, which the Trump administration has argued for. 

“Plaintiffs’ policy arguments about election integrity and voter confidence are properly directed to legislatures, not courts, and regardless, plaintiffs’ definition of ‘election’ would do little to address the concerns they identify,” Ms Barrett added. 

Meanwhile, in a dissenting opinion, Mr Alito said, “Election day is a specified date, not a span of multiple days. The election-day statutes require that federal elections occur on that date. 

“Under the challenged Mississippi law, however, the collection of ballots continues for five more days, and therefore the ‘election’ is not held until the end of that period.”