According to the justice department Apple has used its control of the iPhone to illegally limit competitors and consumer options by preventing the growth of new apps and reducing the appeal of competing products.
It’s significant complaint, which Apple has said it will content "vigorously" and alleges that Apple used "a series of shapeshifting rules" in a bid to "thwart innovation" and "throttle" competitors.
Attorney General Merrick Garland said that Apple, "undermines apps, products and services that would otherwise make users less reliant on the iPhone".
The complaint lists a number of "anti-competitive" steps that include blocking apps, suppressing mobile cloud streaming services, limiting third-party digital wallets and "diminishing the functionality" of smartwatches not made by the company.
Consequently, Apple is accused of making life extremely difficult and expensive for both users and developers who look to venture outside the Apple ecosystem.
So, what happens if this complaint succeeds?
Apple would have to alter contracts and may have to undertake some significant structural changes within the company.
Fred Sainz, a spokesman for the company said that the lawsuit was "wrong on the facts and the law" and that Apple would "vigorously defend against it".
"The lawsuit threatens who we are and the principles that set Apple products apart in fiercely competitive markets," Mr Sainz said. "If successful, it would hinder our ability to create the kind of technology people expect from Apple."
And that’s the rub! The balance that needs to be struck between innovation and competition.
It’s not the first time Apple has faced legal action – since 2009 three legal actions have been brought against it – and the company has been heavily criticised over its iOS ecosystem and through its business practices.
Last month it was fined €1.8bn (£1.5bn) by the EU for breaking competition laws over music streaming.
Apple is set to appeal that fine and will obviously look to fight the legal action brought by the US authorities.
But this is a significant lawsuit. It raises real concerns about the tech sector and the market dominance of the big tech companies.
