D operates over 1,500 retail grocery stores in 40 States. Its 252 stores in California made it the fourth largest supermarket chain in that State. Lucky Stores, Inc. (Lucky), was the largest, with 340 stores. The second and third largest, Von's Companies and Safeway Stores, were merged in December 1987. D notified the Federal Trade Commission (FTC) that it intended to acquire all of Lucky's outstanding stock for a price of $2.5 billion. D and the FTC worked out a consent order, and D accepted the terms. D acquired and paid for Lucky's stock and consummated a Delaware 'short-form merger.' P filed this action alleging that the merger violated §1 of the Sherman Act, and §§ 1, and 7 of the Clayton Act. P sought a preliminary injunction requiring D to hold and operate all of Lucky's California assets and businesses separately pending final adjudication and an injunction requiring American to divest itself of all of Lucky's assets and businesses in the State of California. The District Court granted a temporary restraining order and, eventually entered a preliminary injunction. The court concluded that P had proved a prima facie violation of §7 of the Clayton Act. The Court found that P had made an adequate showing 'that Californians will be irreparably harmed if the proposed merger is completed,' and that the harm suffered 'far outweighs' the harm that D will suffer as the result of an injunction. The court rejected D's argument that the requested relief was foreclosed by a prior decision of the Court of Appeals for the Ninth Circuit holding that divestiture is not a remedy authorized by § 16 of the Clayton Act. D filed an interlocutory appeal pursuant to 28 U.S.C. § 1292(a)(1). The Court of Appeals set aside the injunction reasoning that its own prior decisions established both that ''divestiture is not an available remedy in private actions under § 16 of the Clayton Act,'' and that 'section 16 does not permit indirect divestiture, that is, an injunction which on its face does not order divestiture but which has the same effect. It ruled that the District Court erred by concluding that the 'FTC's consent order' undid 'the legal effect of this merger' which 'had already taken place' according to Delaware corporation law. The Supreme Court granted certiorari.