A Pennsylvania law which imposed liability on ISPs for blocking access to child pornography was struck down by the U.S. District Court last week. The law created criminal penalties for ISPs that failed to censor child pornography on sites they hosted, but in practice, the law resulted in wider suppression of legal sites. According to this Washington Post story, more than 1 million legitimate sites were blocked because of 400 offending ones. The court declared the law unconstitutional (and cited a this paper by Berkman Professor Jonathan Zittrain in the decision). Read the full decision and more about the Center for Democracy and Technology's challenge to the law.