At the heart of the complaint is the so-called "Apple tax", a 30% fee on apps in the App Store that has also prompted a complaint to the European Commission by streaming music rival Spotify. During oral arguments a year ago, conservative Justice Samuel Alito questioned if the precedent that Apple cited now "stands up" in the digital ecosystem. The Motley Fool owns shares of and recommends Apple and Netflix. Apple has argued that developers are the ones who set prices, and that it's not in violation of any antitrust laws.
The court has not declared Apple monopolists yet, but this ruling does allow the case to proceed.
Kavanaugh's stance with the liberal wing of the court was striking.
The case against Apple began when a handful of iPhone owners sued the company on the grounds that it was unlawfully monopolizing the aftermarket for apps. The iPhone giant said it only acted as the intermediary, providing a storefront where consumers found and purchased the apps they later installed on their phones.
The court on Monday agreed with the consumers.
"In the retail context, the price charged by a retailer to a consumer is often a result (at least in part) of the price charged by the manufacturer or supplier to the retailer, or of negotiations between the manufacturer or supplier and the retailer", Kavanaugh said.
Justice Neil Gorsuch, Trump's other pick, wrote the dissent for four conservative justices in the Apple case.
Apple did not immediately respond to a request for comment on the ruling. Apple also claimed that because they don't set the retail price of the apps on the store, iPhone users can not sue them. So leaving new customers without software support after only a few months since they purchased their devices could lead to more frustration among buyers.
Apple, which was also backed by the U.S. Chamber of Commerce business group, had sought to dismiss the case, arguing that the plaintiffs lacked the required legal standing to bring the lawsuit.