Henrik Spang-Hanssen is Danish Supreme Court attorney-at-law and has since 1999 done research mainly on Cyberspace Jurisdictional questions at Santa Clara and Stanford Universities, California. His book deals with Public International Law on Jurisdiction and Cyberspace. The first part deals with the technicality of firewalls and filters on public international computer networks, anti-censorware, censoring and efficiency of filters. The second part deals with public international law on jurisdiction and public international computer networks, especially if it is possible to divide Cyberspace into present jurisdictions by use of software, in particular firewalls and filters. Amongst others, it deals thoroughly with the schism in the Yahoo! Inc. case about a business website accessible in France but made for Americans. A French court has issued an order to Yahoo! to reengineer its websites so Frenchmen cannot see what France regards as harmful and illegal material on Yahool's American websites. Yahoo! has asked California courts to determine that the French order is not enforceable in the United States.