China's internet censors have been working overtime again. PC makers have been told to add internet filtering software to every machine sold in the country from Wednesday and Google has been ordered to cut off access to foreign websites from its local Chinese service.

Though done in the name of fighting pornography, these measures would also give the censors far greater powers to limit information and communication they find politically inconvenient.

The trade complaint that the US levelled last week against the PC software, Green Dam-Youth Escort, represents one welcome development in the resistance to censorship. China's clampdown on the free flow of information has often smacked of protectionism. No doubt that reflects a view in Beijing that local technology suppliers and internet companies will be more compliant when the censors call, and makes it all the more important that China is held to its international obligations.