The U.S. Supreme Court on Monday declined to block a lower court ruling that forces Google to significantly revamp its Android Play Store, following a jury decision that found the tech giant had operated an illegal monopoly.

In a brief, one-line order, the Supreme Court rejected Google’s request to pause a mandate issued nearly a year ago by U.S. District Judge James Donato. The judge's ruling requires Google to make sweeping changes to how it operates its app marketplace on Android devices — which dominate the smartphone market outside of Apple’s iPhones.

Key among the changes: Google must open up its entire catalog of Android apps to competing app stores, and allow these rivals to be accessed and downloaded directly through the Play Store.

Google warned in a recent filing that this requirement would put over 100 million U.S. Play Store users at risk, claiming it could open the door to malicious or pirated apps. The company also said it would be forced to begin complying with the order by October 22 unless the Supreme Court intervened.

Despite its objections, Google said it will begin implementing the required changes while continuing to challenge the ruling. “We believe the District Court's order compromises user safety,” the company stated.

Google had previously managed to avoid implementing the changes while it appealed both the monopoly verdict and the judge’s order. But that strategy hit a wall two months ago when the Ninth Circuit Court of Appeals rejected Google’s bid for a stay.

In its Supreme Court petition, Google argued the ruling unfairly compels it to act as a distribution platform for its competitors. However, Judge Donato said Google's exclusive grip on the Play Store — and particularly its control of in-app payments — gave it an unfair advantage and resulted in billions of dollars in annual profits.

At the heart of the legal battle is the 15–30% commission Google collects on in-app transactions. This fee structure was a central issue in a 2020 antitrust lawsuit brought by Epic Games, creator of Fortnite. That case led to a month-long trial in federal court and ultimately a jury verdict against Google.

While Epic lost a similar legal fight against Apple — with a judge ruling that the iPhone App Store was not a monopoly — Apple was still ordered to permit developers to link to other payment methods. That move led to further legal conflict, including Apple being held in contempt of court earlier this year.

Epic CEO Tim Sweeney praised the Supreme Court's decision on Monday, saying it would give consumers the freedom to choose different payment options “without fees, scare screens, and friction.”

Though the changes may reduce Play Store revenue, Google’s primary earnings come from its massive digital advertising business, built around its dominant search engine. That part of its empire is also under pressure: the U.S. Justice Department has declared both Google Search and segments of its ad tech operations illegal monopolies.

In one DOJ case, a judge earlier this year rejected a proposal to break up Google’s search business — a decision widely seen as a temporary win for the company. Meanwhile, a separate case focused on Google's ad tech is ongoing, with final arguments set for November 17 in Alexandria, Virginia.