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.

The order to put Green Dam on to every PC puts manufacturers in the position of having to load untested, allegedly insecure software on to their machines and could expose them to extra service and liability costs. Anything like this that makes it harder for foreign PC makers or internet companies to do business inside China, or that may favour local competitors, should rightly be resisted.

But unless there is a change of heart in Beijing, the buck, ultimately, will stop with the companies themselves. As Google’s latest troubles in China show, appeasing the censors to gain market access – something it did by acceding to self-censorship when it set up a local search service – does not buy immunity. Google appears to have resisted the latest demand from Beijing. That it is showing signs of standing up to the bullying is a welcome development.

PC makers now face a similar decision about whether to submit to demands to carry the invasive Green Dam software. The demand could be a first step towards turning PCs, which have played a central role in the information revolution, into clients of the state.

There is still time for Beijing to have a change of heart. It should realise that a country that aspires to join the modern information economy cannot afford the chilling effect of slapping restrictive software on every personal computer. But if it does not relent, foreign computer makers should draw a line at this unwarranted extension of government information control and refuse to go along.