The Cyberspace Electronic Security Act (CESA) was passed in 1999, and it gives law enforcement the right to gain access to encryption keys and cryptography methods.
The initial version of this act allowed federal law enforcement agencies to secretly use monitoring, electronic capturing equipment, and other technologies to access and obtain information.
These provisions were later stricken from the act, although federal law enforcement agencies were given a large amount of latitude to conduct investigations relating to electronic information.
This act generated much discussion about what capabilities law enforcement should be allowed to use in the detection of criminal activity.
NOTE: One problem with the act is that it does not have any mechanism for law enforcement to obtain encryption keys. They are not necessarily stored with a third party.
The law simply states that if a third party has encryption keys, law enforcement officials can request a subpoena to demand such keys if they can convince a judge of probable cause.