With regard to the fear that the issuance of your 'Klinton Key' will allow your favorite TLA to decrypt all conversations taped previous to the issuance of the warrant granting the key, there is precedence that disallows it. [citations deleted]
It is true that evidence from an illegal wiretap cannot be used as evidence in court; this is called the Exclusionary Rule. While the ER has been weakened in the last decade, it still basically holds. Unfortunately, that is not where the main threat lies. Exploratory wiretaps, illegally made and whose evidence is not directly admissible, provide information that may lead investigators to other information. This secondary information _is_ admissible. It would be a wonderful if the ER were strengthened so that all evidence which resulted from an illegal search _and all of its subsidiaries_ were conidered tainted. That battle, however, is a much longer one to fight. Even in that situation, though, the defense would have to prove that an unauthorized wiretap took place. Eric