Bill Baer, the head of the Justice Department's Antitrust Division, said the ruling "reinforces the victory the department has won for consumers.”
"Consumers will continue to benefit from lower e-books prices as a result of the department’s enforcement action to restore competition in this important industry," he said in a statement. "By appointing an external monitor to ensure future compliance with the antitrust laws, the court has helped protect consumers from further misconduct by Apple."
The Justice Department first accused Apple and five e-book publishers of price-fixing last year.
The five publishers — Macmillan, Penguin Group, Hachette, HarperCollins and Simon & Schuster— all settled with the Justice Department, leaving Apple as the only company to fight the charges in court.
After a three-week trial, Judge Denise Cote found Apple guilty in July, concluding that it "played a central role in facilitating and executing" a conspiracy to stifle competition from Amazon and raise the price of most e-books by two or three dollars.