The Digital Millennium Copyright Act (DMCA) is a draconian law that prohibits “circumventing” DRM and “other technical protection measures” protecting copyrighted works according to the EFF (Electronic Frontier Foundation). Once every 3 years the Copyright Office accepts applications for exemptions from the DMCA clause. Previously this covered such allowed uses as unlocking cellphones and other ways users could make full use of the devices they purchased.
The biggest issue raised was the issue of “Jailbreaking” cellphones like the iPhone. The Copyright Office rejected Apple’s claim that copyright law prevents users from installing unapproved applications:
When one jailbreaks a smartphone in order to make the operating system on that phone interoperable with an independently created application that has not been approved by the maker of the smartphone or the maker of its operating system, the modifications that are made purely for the purpose of such interoperability are fair uses.
You can read more about the ruling on the EFF website at this link or read the full rulemaking order PDF at this link. The full PDF is really interesting since it gets to the root of the arguments back and forth.