Child porn laws cast a wide web.

• Position: Trends And Transitions

Child pornography is illegal, but the volume circulated on the Internet is staggering and the number of people obtaining, trading and distributing these images is downright appalling." That was the assessment of Michael Heimbach, chief of the FBI Crimes Against Children Unit, in testimony to a congressional committee in 2002.

That same year, the Pennsylvania legislature passed a law requiring in-state Internet service providers to block access to Web sites containing child pornography. The American Civil Liberties Union (ACLU) and the Center for Democracy and Technology (CDT) have challenged this law as unconstitutional under the First Amendment. They allege the law requires blocking access to many Web sites that have nothing to do with child pornography.

In the CDT's view, the problem is that compliant service providers must block access to Web servers they do not host. A single Web server may host thousands of other sites, and such a block makes those other inoffensive sites inaccessible. "It would be as if mail delivery for an entire apartment building were stopped because one tenant was accused of wrongdoing," says John Morris, CDT staff counsel.

A federal judge agreed in September, overturning the Pennsylvania law on the grounds that the tools to block child pornography sites also cause "massive suppression" of constitutionally protected speech.

Pennsylvania defends the law by arguing that there are other cheap and effective ways to narrowly target offending Web sites.

A 2003 Oklahoma law follows a narrower approach...