Rooting and Jailbreaking have, for the longest time, found itself in a legal grey area. Proponents maintain the position that since they own their devices, they can alter them as they please. And opponents (usually large corporations) believe their technology would be at risk if users could alter their phones at a "superuser" level. The Digital Millenium Copyright Act (DMCA), the legislation specifically designed to deal with issues such as this, had never addressed the phone "hacking", until now. Today, a slew of DMCA exemptions were added, one of which exempted rooting/jailbreaking from being considered "copyright infringement."
Continue reading the entire article here: Library of Congress updates DCMA, jailbreaking/rooting is officially 'legal' - iPhone 4 Forum
Source: Wuyanks, iPhone4Forum.net