Plummer, nominated for a best supporting actor Oscar for his role in "Beginners," will Supreme Court Associate Justice John Marshall Harlan II. (He has already won a Golden Globe and Screen Actors Guild Award for his "Beginners" role.) Langella will play Chief Justice Warren Berger.
Shawn Slovo wrote the script, which recounts Ali's legal case going to the Supreme Court. The champ was arrested, found guilty on draft evasion charges, and stripped of his title, though he was not imprisoned as he appealed his conviction.
During the struggle he delivered some of his most enduring quotes, including, "I ain't got no quarrel with them Viet Cong… No Viet Cong ever called me n—–" and "How can I shoot them poor people? Just take me to jail."
Ali has not yet been cast.
Plummer and Langella's castings were first reported by Variety.