Givens is a scriptwriter and a member of the Writers' Guild of America (WGA). Givens wrote a script titled The Fourth Estate a/k/a/Final Edition (Final Edition). Westwind optioned Final Edition for the purpose of securing a television broadcast commitment from a network. Under the agreement between Givens and Westwind, any writing credit to be accorded Givens was to be determined pursuant to the WGA's credit-determination procedures. Givens was entitled to additional compensation under the contract only if the WGA awarded him a 'written by' or 'screenplay by' credit. D acquired the broadcast rights to Final Edition (First Agreement). D then bought all rights to Final Edition from Westwind and Givens. The Second Agreement provided that, 'if a project is produced based upon the literary property, CBS agrees . . . to provide credit Ps as Co-Executive Producers (or Executive Producers at CBS' election) on a shared card.' The Second Agreement also incorporated the provision in the original contract between Givens and Westwind stating that any writing credit for Givens would be governed by the WGA's credit-determination procedures. When the Notice of Tentative Writing Credits was issued, Givens was not listed as a 'participating writer' who was entitled to receive credit. Givens complained to the WGA. The WGA responded by suspending the credits process and informing Columbia Tristar, one of the producers of Early Edition, that if Early Edition aired with credits different from those that the WGA ultimately found to be proper, the WGA would pursue damages on behalf of the WGA-credited writers. The WGA concluded that Givens was not a 'participating writer' of Early Edition. On reexamination, The WGA reaffirmed its conclusion. While Givens was pursuing his WGA appeals, Ps filed this action. They argued that the Early Edition project was 'based upon' the literary property Final Edition and that, accordingly, D had breached its contract by not providing them with writing and production credit. D removed to federal court, and D then filed a Notice of Initiation of Arbitration, which sought a decision pursuant to the WGA's arbitration procedure. The district court stayed proceedings in federal court pending the outcome of the arbitration. WGA ruled in favor of D. Givens stipulated to an order confirming the arbitration award. Accordingly, Givens is not a party to this appeal. D then filed a motion for summary judgment against Ps. D asserted that the formal WGA arbitration had a preclusive effect on Ps' federal action. The district court rejected that argument and granted summary judgment on the alternate ground that the earlier WGA participating-writer determination involving Givens had a nonmutual collateral estoppel effect. Ps appealed.