SEX is off the menu on Compuserve. Parents, in particular, may welcome the American company's decision to block access to 200 sexually explicit sites on its Internet database in response to a ruling by a German court. The absence, until now, of any controls has made it easier (and cheaper) for minors to surf the Internet in search of forbidden fruit than to sneak off to some none-too-careful newsagent.

The move may not be very effective. Other Internet servers will still carry offensive material, which the determined surfer will be able to track down while Compuserve examines its options. But the ruling that certain sites breach German anti-pornography laws raises more fundamental concerns. Precisely because there are no international frontiers on the net, the ruling implies a de facto extra-territoriality not only to German law, but to the laws of any country that tries to control what its own citizens may see. To prevent pornography in Germany, Compuserve has been forced to block access to users worldwide.

The judgment also sets a more sinister precedent. Totalitarian governments could abuse it to deny their own, and other countries' citizens, the right to access material critical of the regimes anywhere on the net.