The Librarian of Congress recently decided in their triennial DMCA exemption rule-making process to remove the existing exemption that allowed individuals to unlock their own mobile phones to use on the compatible network of their choice. As a result of this decision, individuals no longer have clear immunity to unlock new phones - thereby putting them in potential legal jeopardy. I succeeded in petitioning for this exemption in 2006 when I was with the Center for Internet and Society and in 2009 when I was with the Electronic Frontier Foundation -- it's very disappointing to see that work reversed now.
Unlocking phones is commonly used for international travel including by our service members who deploy abroad. Until recently, T-Mobile encouraged potential customers to unlock their phones and sign up with that service. The recent ruling raises barriers to changing network providers -- protecting particular dominant players, violating individual property rights and potentially resulting in individuals being sued or arrested for what they do with their own devices. Unfortunately this may also lead to more phones ending up in landfills and polluting our planet because the locked phone is useless to people here or in other countries who otherwise could make use of an unlocked device on their domestic telecom providers' networks.
While it's still unclear how this ruling will be interpreted and enforced there is a movement to reverse this decision or have a Congressional bill to permanently fix this problem - to join in that effort sign their White House petition here. They are currently at 82,000 signatures but have to get to 100,000 signatures by Saturday.
You can read two articles on this issue by Derek Khanna, the previous Congressional staffer for the House Republicans who authored the viral memo on copyright reform, who is spearheading some of the activism on this issue (here and here). Sina Khanifar is the creator of the petition and also spearheading this issue. He personally received a cease and desist notice for selling services to unlock phones (and, full disclosure, at the time I represented him pro bono).