Fox (P) operated a movie theatre in San Bernardino. P's contracts with movie distributors gave it the exclusive right to show first-run movies in the San Bernardino area for a period of time. D built a theatre eleven miles away and notified P that its contracts were a violation of antitrust laws. Fox (P) claimed that D's notification together with threats of lawsuits gave rise to duress and coercion. P claimed that it was deprived of its rights to negotiate for first run contracts. P asked for declaratory relief (the contracts were not in violation of the antitrust laws), and an injunction against an antitrust action by D. D filed a counterclaim; there was no substantial competition between the two theatres making the clearances under the contracts unreasonable. D alleged that a conspiracy existed between P and its distributors to restrain trade and monopolize first-run movies in violation of the antitrust laws. D sought treble damages and demanded a jury trial under FRCP 38(b). The district court found P's prayer for declaratory relief an equitable action and directed that these issues be tried without a jury before a jury would determine the validity of D's antitrust charges. D sought mandamus to require the judge to vacate his trial order. The Ninth Circuit denied the writ holding that the district judge acted within the proper scope of his discretion. The Supreme Court granted certiorari.