(Bloomberg) -- The judge presiding over Epic Games Inc.’s challenge to Google’s Play Store business model said he’s not confident about setting a fee for mobile app developers without expert input.

A jury last month sided with the maker of the popular game Fortnite and concluded that Alphabet Inc.’s Google Play unlawfully abused its power in what has become a duopoly with Apple Inc. that generates close to $200 billion a year. In the next phase of the case, US District Judge James Donato will decide on a remedy.

“I have grave doubts that I am in any position to set a fee that developers might pay,” Donato said at a hearing Thursday as he discussed the litigation’s next steps with attorneys. “That’s beyond the canon of Article III judges.”

The verdict handed down by a San Francisco jury on Dec. 11 threatens billions of dollars in revenue for Google Play, which charges commissions of as much as 30% to software developers who typically have few other options.

At the time, Epic Chief Executive Officer Tim Sweeney said his company would seek “actual changes in practice” to Google’s app store, but didn’t provide specifics about a potential remedy.

Donato said he will give Epic and Google a chance to negotiate a settlement, and if they can’t come an agreement, he’ll hold a hearing in mid-March. The judge signaled that he wants input from expert economists.

Epic largely lost a similar challenge to Apple’s app store in 2021. Both companies asked the US Supreme Court to review the dispute but the justices this week declined, without explanation.

In December, Alphabet agreed to pay $700 million to settle separate antitrust complaints brought by state attorneys general and consumers challenging Google Play policies. 

Corie Wright, Epic’s vice president of public policy, criticized the deal because it doesn’t limit the fees charged by Google. The accord instead calls on Google to change its Play Store policies to reduce barriers to competition for app distribution and payment processing.

Read More: Google Play Deal Frustrates Critics of Steep App Developer Fees

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