Australia's main news publishers are responsible for comments that readers post on their corporate Facebook pages.
That was the ruling made by the country's High Court on Wednesday (September 8).
The court dismissed an appeal against a previous case that had found in favour of a defamation suit brought by Dylan Voller, who'd been the subject of several news reports about youth detention.
The lawyer - Patrick O'Brien - said the ruling would protect people from online abuse.
"What that means for people who might be vulnerable to social media mob attacks, they're protected essentially by this decision, because it means that the media companies bear responsibility for those posts."
Voller argued that stories posted on the news companies' Facebook pages had led to third-party users making defamatory comments about him.
He alleged the news outlets, including Fairfax Media and others, were liable as the publishers.
He filed a suit and the court found in favour of Voller.
At the time the comments were posted, Facebook did not allow page moderators to turn off comments on posts - it has since changed that.
A spokesperson for major Australian broadcaster Nine said it was 'disappointed with the outcome'.