This is a thorny area. Establishing the precise link between violence on television and violent behaviour is difficult. Even if we accept that there is a link, establishing a consensus on a ratings system would be tortuous. Agreement might be possible on the extremities of fictional violence, but then some of the most violent and horrifying films - Seven, for instance - do not show acts of violence, just some of the results. Beyond that, agreeing on acceptable standards of swearing and sex would be even more difficult.
Even more problematic is the way a V-chip would be quickly outflanked by technology and children's adeptness at using it. The technology of communications cannot be controlled. It respects no national boundaries, social codes or generational precedence. Young children can programme videos and dial up Web pages at the outer limits of the World Wide Web with a skill that leaves adults in their wake. The new American law is already out of date. It may not cover the television cards that can turn a desktop computer into a television receiver; it does not cover the way television pictures are becoming available over the Internet.
But none of this excuses fatalism. It is adults who pay for their children's surfing habits on the Internet. Adults read Radio Times. It is adults who need to think more clearly about what is fit for viewing or downloading. Welcome efforts are already being made to make exploration of the Internet safer for children by using "system invigilators" that patrol the boundaries of zones which parents might judge unsuitable for children.
As for television, the V-chip can only be "another tool" in parents' hands, as Lady Howe of the Broadcasting Standards Council put it. It cannot substitute for the time and effort good media parenting require. What it ought to do, however, is open up a debate and help us to refine our thinking about suitability, about the kinds of violence that young viewers ought to be exposed to.
The V-chip only works if broadcasters have agreed a ratings system. One is needed, and one a lot more sophisticated than the existing 9pm "watershed" or the system cinema and video distributors use. That is going to be difficult, but it is high time a start is made.