Justice Brett Kavanaugh wrote the majority opinion, which was joined by the court's liberal justices.

The iPhone users argued that Apple's 30% commission on sales through the App Store is an unfair use of monopoly power that results in inflated prices passed on to consumers.

Apple argued that only app developers, and not users, should be able to bring such a lawsuit. But the Supreme Court, in an opinion authored by Kavanaugh, rejected that claim.

"Apple's line-drawing does not make a lot of sense, other than as a way to gerrymander Apple out of this and similar lawsuits," Kavanaugh wrote.

Shares of Apple, already battered by trade concerns, were down 5%, lagging the broader market.

The result was widely expected after arguments in November in the case, Apple v. Pepper, during which the justices seemed skeptical of Apple's arguments.