A Federal Court has blocked Penguin Random House’s acquisition of rival Big Five publisher Simon & Schuster. At press time, Judge Florence Y. Pan’s opinion was not yet public as the parties still need to agree on redactions to protect confidential information, but in a brief two page order Pan enjoined the merger.

“Upon review of the extensive record and careful consideration of the parties’ arguments, the Court finds that the United States has shown that ‘the effect of [the proposed merger] may be to substantially lessen competition’ in the market for the U.S. publishing rights to anticipated top-selling books,” Pan’s order states. “Accordingly, judgment shall be entered in favor of the Plaintiff and the merger shall be enjoined.”

The parties now have until November 4 to file proposed reactions, after which the court will issue a public version of Pan’s Memorandum Opinion.