The Digital Millennium Copyright Act bans people from circumventing a "technological measure" to gain access to a copyrighted work.
The law instructs the Librarian of Congress to grant exemptions to the ban. In 2006 and 2010, the Librarian of Congress exempted cellphone unlocking from the law's restrictions, but last year the agency allowed the exemption to expire.
CTIA, the wireless industry's trade group, told the Library that the locks help ensure that people do not buy a heavily subsidized phone from one carrier and then switch to a competitor's network before the contract is fulfilled. The group also said that the industry is plagued by large-scale phone trafficking in which people buy prepaid phones, unlock them and resell them overseas.
The group argued that carriers already sell many phones that come unlocked, but critics argue that the majority of phones are still permanently locked to one carrier.
The opponents of the ban argue that people should not have to buy a new phone to switch carriers even after they have fulfilled their contract.
The Library of Congress is an independent legislative branch agency, and it is unclear what power President Obama has to reverse its decision, even if he agrees with the petition.
The petition urges the White House to ask the Librarian of Congress to rescind its decision or to champion a bill that makes unlocking phones legal.