CALEA is the Communications Assisance for Law Enforcement Act of 1994 designed to help law enforcement easily intercept communications. In present day, Voice-over-IP (VOIP) technology is gaining widespread use so now CALEA has made its way into this new realm. VOIP providers now are forced to comply with CALEA or face tough penalties.
VOIP is not intrinsically secure, encryption is a optional and most major providers do not seem to offer a suitable encryption solution. There seems to be some ambiguity to which providers are currently compliant with CALEA laws so we have (special thanks goes to Co-developer Raven) for putting together a extensive list of companies that are compliant with CALEA. The list may be obtained here