The details of the ruling were made public 60 days after the Milan court acquitted three Google executives of charges of having violated the privacy of an Italian boy with autism by allowing a video, showing him being bullied, to be posted on the site in 2006.
The decision in December overturned a previous court ruling in 2010 which had sentenced the executives to a six-month suspended jail sentence, reigniting a debate about privacy over the Internet.
"The possibility must be ruled out that a service provider, which offers active hosting can carry out effective, pre-emptive checks of the entire content uploaded by its users," the court said in the public ruling reviewed by Reuters.
"An obligation for the Internet company to prevent the defamatory event would impose on the same company a pre-emptive filter on all the data uploaded on the network, which would alter its own functionality."
The case arose in 2006 when four students at a Turin school uploaded a mobile phone clip to Google Video showing them bullying the boy.
The prosecutors accused Google of negligence, saying the video remained online for two months even though some Web users had already posted comments asking for it to be taken down.
Google said it had removed the video immediately after being notified and cooperated with Italian authorities to help identify the bullies and bring them to justice.
Googles has always maintained that, as hosting platforms that do not create their own content, Google Video, YouTube and Facebook cannot be held responsible for content that others upload.
© Thomson Reuters 2013