A spokesperson forThe Sydney Morning Herald said it was"reviewing the judgment and considering its options following today’s decision and the implications the ruling may have on the industry".

In 2018,the South Australian District Court held a former political candidate,Mark Aldridge,liable for defamatory comments made on his Facebook page,in circumstances where he had previously been asked to remove the comments.

Mr Voller's lawyers had argued the media defendants had the power to remove or hide the comments,and could have chosen to monitor the comments but did not do so.

The media organisations argued they did not publish the comments,had no liability for them,and were not contacted by Mr Voller and asked to take them down.

Justice Rothman said the media organisations'public Facebook pages were not merely"a conduit of the comment"and operated for commercial purposes,which encouraged publication of comments.

"Moreover ... each defendant was aware that comments on its initial posting were likely and more probably than not would include defamatory material,"Justice Rothman said.

He said the organisations could have hidden all comments on their pages by filtering a series of common words,and there seemed to be no public policy reason why liability should not be"sheeted home to the media company".

"It is the comment's presence on the public Facebook page which allows all third-party users to gain access,"Justice Rothman said.

"If the comment were made on the commentator's own private Facebook page,only her or his friends would view it and probably none of them would look for it or find it."

Justice Rothman found extended publication of the comment was"wholly in the hands of the media company that owns the public Facebook page".

He said the media outlets continued to operate public Facebook pages for their"own commercial ends"and by doing so had assumed the risk that comments made on those pages would"render[them] ... liable under various laws that may prevent,render unlawful,or render actionable in damages various statements".

The judgment is one of the first times an Australian court has ruled on the liability of Facebook page owners for comments left by others. Previously,only those who posted the comments on Facebook or who failed to remove the comments after being told about them were liable.

Justice Rothman acknowledged his decision would likely trigger an appeal in a higher court.

"It is fair to say that the issues before the court in this matter relate to an emerging area,"he said.

In a statement,Mr Voller's lawyer Peter O'Brien said the decision was a"significant win"for his client and"others who may find themselves an object of public scrutiny".

"We are very happy with the judgment as it clarifies the law around social media platforms and paves the way for a broader understanding of how defamation proceedings can protect people in the context of new technology,"Mr O'Brien said.