Back in 2010, an exception was added to the United States’ Digital Millennium Copyright Act by the Librarian of Congress that made it perfectly legal to jailbreak, unlock, or install unapproved third-party apps on any hardware (at the time, the exception was added with a focus on the iPhone, though it currently applies to any device). However, a change noted by Tech News Daily in the DMCA means that starting this Saturday, unlocking a phone through unofficial means will become illegal in the United States.
The change was made back in October of 2012 by the Librarian of Congress, though at the time a 90 day windows was offered before the update was legally in effect.
This change will affect users of every platform, as many users unlock their devices in order to take them to other carriers. While most US carriers already forbid this, the issue could never be charged as criminal. With this change, carriers now technically have the option to file charges against anyone who unlocks their device. That is unlikely to happen, though it still is worth keeping in mind.
AT&T offers customers the option to unlock their device after their contract has run out, though this will certainly put a damper on the various iPhone unlocking websites available.
Already, a petition is available for those wishing to protest this change. Available through WhiteHouse.gov, the petition demands that unlocking a cellphone be legalized.