Supreme Court said of CDA:

Unnecessarily interfered w/ 1st Amendment right of adults to communicate with each other
Vagueness of terms “indecent,” “patently offensive” which covered large amounts of non-pornographic material with serious educational & other value
Because of Internet communications can be transmitted anywhere, local community standards would allow a communication to be judged by that community in the U.S. most likely to be offended by the message