UPDATE: An appeals court in Milan acquitted today three Google executives of violating the privacy of an Italian boy with autism, in the so-called “Vividown” case. “We’re very happy that the verdict has been reversed and our colleagues’ names have been cleared. Of course, while we are delighted with the appeal, our thoughts continue to be with the family who have been through the ordeal,” said Giorgia Abeltino, Google Italy Policy Manager, in an statement.

The European Union Directive on electronic commerce is not the most inspirationally named document. The title would barely fit on a placard, and scans awkwardly for sloganeering (“What do we want?” “Implementation of the Electronic Commerce Directive!” “When do we want it?” “Within an agreed scheduled framework period, subject to negotiation between neighbour states and key stakeholders!”)

But the eCommerce Directive, as it is known by, er, some people, states a principle that is absolutely crucial to how the web works.

Article 12 of the directive, adopted in 2000, establishes the principle of the “mere conduit”. That is the idea that an Internet Service provider is not liable for content hosted on its platform, provided it “(a) does not initiate the transmission; (b) does not select the receiver of the transmission; and (c) does not select or modify the information contained in the transmission.”

This idea means that, at least in theory, Facebook, YouTube etc. can allow users to post anything on their platforms without worrying about having to account for it legally.

I say “in theory”. Today (21 December), an appeal will take place in an Italian court over a ruling which severely tested the concept of “mere conduit”.

In September 2006, Italian secondary school students posted a video of a boy with Down’s Syndrome being taunted and beaten by other teenagers. The video remained online until November that year, when it was removed by YouTube following a request by Italian police.

In 2010, three Google executives were found guilty of breach of privacy by an Italian court in a case brought by Down’s Syndrome charity Viva Down. The appeal comes to court on Friday.

Google protests that it acted as soon as it was notified by the authorities that the video may be illegal. Prosecutors claim that YouTube should have responded to private complaints sooner.

Videos of bullying are unpleasant to say the least, but the people responsible for the harassment of the boy, and the uploading of the video, have been convicted.

The 2010 conviction of Google employeees seriously breaches the idea of ISP as “mere conduit”, and with that, the way the web works. If social platforms are to be held responsible for all content, the consequences could be catastrophic for the way we operate on the web. Even the Chinese Internet police cannot pre-moderate every single piece of content uploaded, which is what ISPs may feel obliged to do should they be held responsible for content. The alternative might be an automated “banned words” list, perhaps. Either way, we would see an enormous escalation of censorship. What’s more, we would be establishing, even more than already exists, a system of privatised censorship. By handing over responsibility for what we say online from individuals to ISPs, we would be allowing private companies even more power than the state has to govern our speech.

Already this week there has been uproar over Instagram’s (attempted, then hastily withdrawn) grab for users’ content, itself perhaps a breach of mere conduit status.

And if this ruling is upheld in Italy, we’ll be facing another blow to individuals’ free use of the web. Already, a huge deal of our communication happens across private networks. If they are legally responsible for every word, picture and video, they will be inclined to caution, and our space to speak ever more narrowed.

Padraig Reidy is news editor at Index on Censorship