Apple is generally expected to ask a judge to prevent the order from coming into effect. Either company could also appeal to the United States Court of Appeals for the Ninth Circuit. In that tribunal, a panel of three judges could review the decision, a process that could take a year or more. After a decision there, Apple or Epic could appeal to the Supreme Court.

The decision allows both sides to claim a partial victory. Apple now has a court ruling that says it does not have a monopoly in a significant digital market, undermining efforts by its opponents to claim it violates antitrust laws. But Epic’s lawsuit could also force Apple to open up its airtight iPhone software to create a way for developers to avoid its commission.

Apple shares fell nearly 3% on the Nasdaq stock exchange after the decision was announced.

“Today, the court confirmed what we have known all along: the App Store does not violate antitrust law,” Apple said in a statement. “As the court recognized, ‘Success is not illegal.’ Apple faces stiff competition in every segment in which we operate, and we believe customers and developers choose us because our products and services are the best in the world. “

The decision upheld many principles of Apple’s App Store business, including the fact that it can ban third-party iPhone app marketplaces and continue to charge a 30% commission on many transactions. Epic had challenged these practices.

“It puts an economic question mark around the App Store, but at the same time, it affirms the principles” of the company, said Adam Kovacevich, a former Google lobbyist who now heads a technology policy group which is partly sponsored by Apple.

Tim Sweeney, CEO of Epic, said on twitter that he was not happy with the decision because it did not go far enough in allowing businesses to transact in-app with their own payment systems, instead of having to direct customers to external websites. He said Fortnite will not return to the App Store until such rules are in place.

“Today’s decision is not a victory for developers or for consumers,” he said. “We will continue to fight.”

Mr Rubin, the antitrust lawyer, said Apple would feel relieved to avoid being labeled a monopoly, but the judge’s verdict would likely not help strengthen its position in other investigations as the lawsuits antitrust may vary. He said Apple might also consider lowering its commission now that it will be easier for developers to send customers elsewhere to make purchases.