The complaint comes as Ticketmaster makes competitive gains in the resale market, where StubHub is currently the biggest player. While primary tickets remain Ticketmaster's biggest business, its secondary ticket transactions volume grew by 55 percent last year, according to Live Nation's 2014 annual report.  Though the current case could potentially hold implications for ticket buyers, StubHub will likely find it hard to prove a monopoly, said Marc Edelman, an associate professor of law at Baruch College who consults on sports antitrust law.  "The antitrust claim overall seems like a very difficult one for StubHub to win," Edelman said.  Read MoreFans to pay a pretty penny for basketball, hockey face-offs  Many sports franchises, including the Cleveland Cavaliers, recommend that fans resell tickets on a particular platform to ensure validity. StubHub's complaint revolves around an assertion that the Warriors revoked or threatened to revoke some season ticket rights because sellers used a resale platform that competes with Ticketmaster.  In a statement to CNBC, the Warriors said they chose not to renew season tickets for some brokers whose "sole intent" was to resell them at a higher price. Those tickets went to fans who had been on a wait list.  StubHub contends that the Warriors threatened would-be sellers, causing its ticket inventory for the team's games to drop by 80 percent from last season to this season.  Ticketmaster declined to comment. In its motion to dismiss the lawsuit, Ticketmaster decried StubHub's claims that a monopoly could exist for only one team's tickets. Ticketmaster noted in the motion that the Warriors only represent a "sliver" of StubHub's business.
As the Warriors tip off the NBA Finals, StubHub is accusing the NBA's best team and Ticketmaster of running a monopoly.