Australia's landmark social media ban for children is being challenged in the nation's highest court, with two teens alleging the law is unconstitutional as it robs them of their right to free communication.

From 10 December, social media firms - including Meta, TikTok and YouTube - must ensure that Australians aged under 16 cannot hold accounts on their platforms.

The law, which is being watched closely around the globe, was justified by campaigners and the government as necessary to protect children from harmful content and algorithms.

However, 15-year-olds Noah Jones and Macy Neyland - backed by a rights group - will argue the ban completely disregards the rights of children.

"We shouldn't be silenced. It's like Orwell's book 1984, and that scares me," Ms Neyland said in a statement.