[Avodah] Restricting a broadcast

[Ben Waxman via Avodah]

Rav Yosef reportedly tried to limit the broadcast of his regular Torah 
class. Anyone wanting to know more can look it up because I don't want 
to get involved in that particular episode.

My question is in a case like this, where a rav is broadcasting on two 
public radio stations, does he have the right to restrict a third? 
Meaning, does his (halachic) copy right extend that far or once he is 
speaking in public and broadcasting the talk, any halachic rights he may 
have towards ownership are lost?

Ben