This is a good example of how the FCC operates as a quasi government agency, with the NAB steering the boat.
This legal document is quite detailed.
http://www.fcc.gov/document/court-opinion-leyse-v-clear-channel-6th-cir
The FCC was empowered By Congress to make up rules to prohibit automated advertising directed at Residential phone lines. Note this is not the “do not call” list maintained by the FTC.
In 2005, the person who initiated the lawsuit against Clear Channel received a recorded phone message that the radio station was having a contest and if you wanted to enter, listen to the radio station and dial a toll free number. Congress gave the FCC the regulatory discretion to make exemptions – and at the request of the NAB exempted unsolicited recorded calls like this one from radio and TV stations – on the principle that the radio station is not selling anything, hence it is not an advertisement.
The courts along the way have agreed – and in general the courts stay out of questioning the rulings of the FCC. One interesting example of this happens when a radio station goes into bankruptcy. Bankruptcy judges are gods with unlimited power, and every once in a while will try to force the FCC to transfer a station license when the recipient has not established that they meet the requirements to operate the station (US Citizen, no felony convictions, wasn’t a prior operator of a pirate station, etc). Those standoffs can get quite tense.