An upcoming ruling on potential antitrust action against Google's search business could have implications for iPhone maker Apple (NASDAQ: AAPL ), according to JPMorgan analysts.

Last year, a U.S. judge ruled that Google had spent billions of dollars illegally to build a monopoly that made it the world's dominant search engine.

The ruling paves the way for several potential changes, including a breakup of Google's parent company, Alphabet (NASDAQ: GOOGL ), by selling the Chrome browser. Such a move could fundamentally alter the world of online advertising, which has long been at the heart of Google's operations.

Crucially for Apple, the Chrome sale could also prevent Google from paying the Cupertino phone maker to be its default search option.

The legal battle over the judge's ruling has lasted nearly a year and could be prolonged further by an appeal to a higher court.

In a note, JPMorgan analysts led by Samik Chatterjee said that while details were limited, they estimated Apple may have received about $28 billion in traffic acquisition fees from Google. Of that, the analysts estimate about $12.5 billion represents payments for traffic generated by U.S. customers.

The strategists noted that the U.S. Department of Justice, which originally filed the lawsuit, and Google have submitted two different reform proposals to the judge. They said both changes could have an impact on Apple.

In one version, the Justice Department's proposal would prohibit Google from paying for distribution, which JPMorgan said was a "worst-case scenario" for Apple — potentially reducing its earnings per share by about 10%.

At the same time, they believe the "best-case scenario" for Apple is Google's remediation plan, which the analysts say would "largely maintain the status quo of payments Apple receives [...]."

But they still see a third option, a middle path between the Justice Department's and Google's remediation plans.

"We see a potential middle ground emerging in the ruling whereby Google could pay Apple, but only in situations where consumers organically select Google as the default general search engine within Apple's search access points, with Apple being compensated for facilitating that traffic acquisition," the analysts wrote.

They added that this would significantly impact Apple's returns, but that "competitive dynamics" in the search market could also provide "offsetting" benefits. Analysts estimate that such an outcome would reduce Apple's earnings per share by a low-single-digit percentage.

The judge in the case is expected to announce a ruling on corrective measures early this month.