CALEA (Communications Assistance for Law Enforcement Act) is a United States federal law that enables the government to intercept wire and electronic communications and call-identifying information under certain circumstances -- in particular, when it is necessary in order to protect national security. CALEA originated in the House of Representatives as bill H.R. 4922 and in the Senate as bill S. 2375. CALEA was signed into law by President Clinton on October 25, 1994.
There are certain exceptions and prohibitions that limit the extent and applicability of CALEA. These limitations are intended to protect private citizens and communications providers from unreasonable government intrusion. For example, carriers are not responsible for decrypting (or ensuring the government's ability to decrypt) any communication encrypted by a subscriber, unless the carrier provides the encryption method and has the knowledge necessary to decrypt the signals. In addition, CALEA does not authorize law enforcement to require or designate specific equipment specifications to be adopted by service providers.