A bill introduced in the U.S. Congress called the Mobile Device Theft Deterrence Act of 2013 would have made it illegal to change the International Mobile Equipment Identity number on a cellphone, but the bill did not pass, according to GovTrack.us. In the United Kingdom, the Mobile Telephones Re-Programming Act of 2002 made it illegal to change an IMEI number, according to the Staffordshire Police.
The IMEI is a unique 15-digit number assigned by the manufacturer and used by service providers to identify and trace mobile devices connected to their networks, states the GSMA. It has been adopted as an industry standard, and since 1993 every authentic device that works on GSM and 3GPP networks has been assigned an IMEI. The Groupe Speciale Mobile Association, an international standards organization, maintains an IMEI database on its website at GSMA.com.
Mobile service providers can blacklist a device and prevent it from operating on their networks if the IMEI number of that device has been reported stolen, is counterfeit or is being used for malice. Government and law enforcement agencies also use the IMEI number to check whether an imported device is legitimate. One way to find the IMEI number of any device is to enter the code *#06# on the keypad, reports the GSMA.