On November 17, 2021, President Joe Biden announced his intent to nominate Mathis to serve as a United States circuit judge of the United States Court of Appeals for the Sixth Circuit; his nomination was sent to the Senate the following day. President Biden nominated Mathis to the seat vacated by Judge Bernice B. Donald, who announced her intent to assume senior status upon confirmation of her successor. The nomination drew controversy, as both U.S. Senators from Tennessee complained that they had not turned in blue slips and said that the White House had not consulted with them. On January 3, 2022, his nomination was returned to the President under Rule XXXI, Paragraph 6 of the United States Senate; he was renominated later the same day.
