CANBERRA, Australia — Australia’s highest court on Wednesday made a landmark ruling that media outlets are “publishers” of allegedly defamatory comments posted by third parties on their official Facebook pages.

The High Court dismissed an argument by some of Australia’s largest media organizations that for people to be publishers, they must be aware of the defamatory content and intend to convey it.

The court found in a 5-2 majority decision that by facilitating and encouraging the comments, the companies had participated in their communication.

The decision opens the media organizations to be sued for defamation by former juvenile detainee Dylan Voller.

Voller wants to sue the television broadcaster and newspaper publishers over comments on the Facebook pages of The Sydney Morning Herald, The Australian, Centralian Advocate, Sky News Australia and The Bolt Report.

His defamation case launched in the New South Wales state Supreme Court in 2017 was put on hold while the separate question of whether the media companies were liable for Facebook users’ comments was decided.

The companies posted content on their pages about news stories that referred to Voller’s time in a Northern Territory juvenile detention center. Facebook users responded by posting comments that Voller alleges were defamatory.

News Corp Australia, which owns the two broadcast programs and two of the three newspapers targeted in the defamation case, called for the law to be changed.

Facebook did not immediately respond to a request for comment.

Voller’s lawyers welcomed the ruling for its wider implications for publishers.