Lawyers for Reddit and a digital rights group opened a High Court case arguing Australia's world-first ban on social media accounts for under-16s breaches constitutional free-communication protections. A ruling against the government could force a rapid rewrite of the policy other countries have watched closely.

Australia's landmark ban on social media accounts for children under 16 faced its most serious legal test yet on Tuesday as a challenge opened in the country's High Court. Lawyers representing Reddit and a digital rights advocacy group argued that the world-first restriction, which has drawn close attention from regulators and lawmakers overseas, oversteps constitutional limits on government power by cutting young people off from avenues of public discussion.

The case centres on arguments that the ban, which forces major platforms to actively block under-16 users or face steep fines, interferes with an implied freedom of political communication long recognised by Australian courts. Government lawyers are expected to counter that protecting children from documented harms linked to heavy social media use, including mental health and safety concerns, justifies the restriction regardless of its effect on younger users' access to platforms.

A ruling against the government would upend a policy several other countries, including some in Europe and Asia, have cited as a possible model for their own youth online-safety rules. Technology companies operating in Australia have largely complied with the ban since it took effect, but a successful challenge could force a rapid rewrite of compliance obligations and reopen debate over how far governments can go in regulating children's access to digital platforms.