[...] under industry pressure, the Library of Congress — which oversees copyright law — agreed to let the exemption lapse as of January 2013, infuriating consumer advocates who say phone owners should be able to do whatever they want with a device once a contract expires. Wireless providers have said digital locks on cellphones protect their business model: phones are often sold at a steep discount in exchange for long-term service contracts. CTIA-The Wireless Association, which represents major wireless providers including AT&T, Sprint Corporation, T-Mobile USA, U.S.