The US Copyright Office ruled this week that "jailbreaking" smartphones is legal in some cases. The term jailbreaking became known for altering mobile phone operating systems in order to install unauthorized applications, primaril

y after the first iPhone and its App Store were released. This decision will cause some re-writing of the Digital Millennium Copyright Act to be altered.

As CNN's Money Blog explains, "jailbreaking iPhones in order to download apps that are unavailable in Apple's App Store had been a legal gray area: Apple technically had the right to request a $2,500 government fine for damages every time a user violated the law that bans 'circumvention of technological measures' controlling access to copyrighted works -- in this case, the iPhone's iOS software."

Apple never requested a fine, but did take measures to ensure that its right to do so remained preserved. The Cupertino-based company filed an objection to the now-approved decision last year. Jailbroken iPhones may still be subject to other company measures - owners of the device lose their warranty after going through the process.

The decision also included legalizing altering mobile phones so that owners can switch between wireless plan providers. Essential use exemption can only apply to the owner of the device, not to another company, service or organization.

Opposition to digital copyright legislation has considered this development a significant improvement in how legal institutions interpret the DMCA and employ Fair Use. According to CNET on Thursday, fair use violates literal copyright law, but in practice has "limited negative impact on the rights infringed." This argument is founded on the tiny proportion of code altered in the case of the iPhone, an interesting legal basis. This form of fair use is referred to as "essential use," and can only be applied to the actual owner of the device, not extended to third parties who may extend their services.