Every three years this exemption was modified a bit, but in 2012, for unexplained reasons, the Librarian of Congress dropped that exemption entirely, meaning that starting in late January of 2013, it was possible to interpret the DMCA to mean that phone unlocking was illegal. In response to this there was a major White House petition -- which got over 100,000 signatures, leading the White House to announce (just weeks later) that it thought unlocking should be legal -- though, oddly, it seemed to place the issue with the FCC to fix, rather than recognizing the problem was with current copyright law.