Former President Donald Trump's allies have criticized Justice Amy Coney Barrett, one of his Supreme Court appointees, following her authorship of a majority opinion that upheld Mississippi's law allowing mail-in ballots to arrive up to five days after Election Day. This decision effectively closed a legal avenue for challenging postal votes, a process Trump has frequently claimed, without evidence, facilitates fraud.

The Supreme Court voted 5-4, with Barrett writing the opinion. She was joined by Chief Justice John Roberts and liberal justices Sonia Sotomayor, Elena Kagan, and Ketanji Brown Jackson. Barrett's opinion stated that election-day statutes do not set a deadline for ballot receipt and therefore do not prevent Mississippi from counting absentee ballots received after Election Day, provided they were postmarked before.

Prominent conservative figures, including Steve Bannon and Megyn Kelly, publicly criticized Barrett's role in the ruling. Bannon, on his podcast, questioned the vetting process for Barrett's nomination, referencing the emphasis on her conservative credentials. Kelly described Barrett as a "turncoat" who "is constantly sitting with the left."

Trump himself characterized the decision as a "tremendous loss" in a social media post and later described it to reporters as "a little bit surprising," expressing concern that it "gives people more time to vote illegally."

Justice Samuel Alito authored a dissenting opinion, joined fully by Justices Clarence Thomas and Neil Gorsuch. Alito argued that historically, "election" meant completing ballot collection on the designated day. Justice Brett Kavanaugh concurred with the core sentiment of Alito's dissent, including his warning about the potential for fraud associated with late-arriving ballots, though he did not endorse all aspects of Alito's reasoning.