Apple´s online marketplace is the sole avenue for apps for its iPhone and other mobile devices, and the company has paid out more than $100 billion to developers since launching the store a decade ago.
Apple shares were trading down $10 at 187.04 by midday.
The Supreme Court is allowing consumers to pursue an antitrust lawsuit that claims Apple has unfairly monopolized the market for the sale of iPhone apps.
The court has not declared Apple monopolists yet, but this ruling does allow the case to proceed. In an earlier hearing, Justices Stephen Breyer, Elena Kagan, and Sonia Sotomayor questioned Apple's reference to the Illinois Brick doctrine, relating to direct versus indirect purchasers.
Kavanaugh's stance with the liberal wing of the court was striking.
The suit could force Apple to cut the commission it charges software developers.
The court on Monday agreed with the consumers.
"If a retailer has engaged in unlawful monopolistic conduct that has caused consumers to pay higher-than-competitive prices, it does not matter how the retailer structured its relationship with an upstream manufacturer or supplier", the opinion said. Gorsuch also was appointed by Trump.
"This court held that an antitrust plaintiff can't sue a defendant for overcharging someone else who might (or might not) have passed on all (or come) of the overcharge to him", Gorsuch wrote.
Rifkin said the alleged overcharges paid by consumers "will be measured in the billions of dollars".
We have reached out to Apple for comment and will update this story with any response.
Robert Pepper and other consumers filed the class-action lawsuit in 2011, but it was struck down. They were supported by 30 state attorneys general, including from Texas, California and NY.
The case is Apple Inc. v Pepper, 17-204.
After a federal judge in Oakland, California threw out the suit, the San Francisco-based 9th U.S. Circuit Court of Appeals revived it in 2017, finding that Apple was a distributor that sold iPhone apps directly to consumers.