Campaigners have welcomed a US ruling that loosens Apple's tight control over what users of its iPhone can do with the device.
In a decision that could ultimately break the monopoly of Apple's own "App Store" for iPhone games and other applications, the US Copyright Office has given legal protection to people who unlock, or "jailbreak", their phones.
The move grants exemptions to digital copyright laws which campaigners said were being used by smartphone makers such as Apple to unfairly limit fair uses of their products. It applies to all smartphone makers, not just Apple.
"Copyright law has long held that making programs interoperable is fair use," said Corynne McSherry, an attorney at the campaign group the Electronic Frontier Foundation, which pushed for the ruling. "It is gratifying that the Copyright Office acknowledges this right."
Apple currently insists that any software developed for its iPhone be downloaded from its App Store, having first been approved by its own executives. Any apps that Apple deems pornographic or technically sub-standard, or which compete with the core functions of the phone, will be barred from sale.
The ruling also allows users to change the wireless service provider. Currently, AT&T is the sole wireless service provider for Apple in the US.
Apple says it just wants iPhone users to have the best experience possible. Jailbreaking invalidates the warranty and may cause the device to become unstable, it said.