"With changes in technology over the last several decades, the ability to easily and economically carry vast amounts of information in electronic form has risen dramatically. The advent of compact, large capacity, and inexpensive electronic devices, such as laptop computers, thumb drives, compact disks (CD), digital versatile disks (DVD), cell phones, subscriber identity module (SIM) cards, digital cameras, and other devices capable of storing electronic information (hereinafter 'electronic devices') has enabled the transportation of large volumes of information, some of which is highly personal in nature. When these devices are carried by a traveler crossing the U.S. border, these and all other belongings are subject to search by the U.S. Department of Homeland Security (DHS) to ensure the enforcement at the border of immigration, customs, and other federal laws. In particular, U.S. Customs and Border Protection (CBP) and U.S. Immigration and Customs Enforcement (ICE) may conduct border searches of such electronic devices as part of CBP's mission to interdict and ICE's mission to investigate violations of federal law at and related to the Nation's borders. CBP Officers and ICE Special Agents conduct border searches of electronic devices to determine whether a violation of U.S. law has occurred."
Department of Homeland Security: http://www.dhs.gov/