TikTok argued in court on Monday that a US law – which would see it banned unless it is sold by ByteDance – would have a “staggering” impact on the free speech of its US users.
The law was prompted by concerns that US users’ data is vulnerable to exploitation by China’s government.
TikTok and ByteDance have repeatedly denied links to the Chinese authorities.
The companies sued to block the legislation in early May, calling it unconstitutional and an effective ban on the speech of its 170 million US users.
A panel of three judges heard its arguments at an appeals court in Washington DC on Monday.
“This law imposes extraordinary speech prohibition based on indeterminate future risks,” TikTok and ByteDance’s lawyer Andrew Pincus told the court.
Concerns around China came up early, with Mr Pincus stating that the firm “is not owned” by the country.
“The owner of TikTok is ByteDance Limited, a Cayman Islands holding company,” he said.
But Judge Sri Srinivasan responded that the firm was “subject to Chinese control”.
Mr Pincus said the US government does not allege any malfeasance has taken place – and the firm was being punished over the suggestion that there might be issues in the future.
But he was challenged on his argument that the law would be an unprecedented ban on a single speaker – and his claim that it would be “unfeasible” to divest the US arm of the firm.
Judge Ginsberg argued the law is “an absolute bar on the current arrangement of control” of the company, not the company itself.
He also said it targeted a group of companies controlled by a so-called foreign adversary, rather than TikTok alone.
Constitutional right
Jeffrey Fisher, representing creators concerned by the law, said it could impede their constitutional right to work with the editor and publisher of their choice – such as TikTok under its current ownership.
TikTok creator Tiffany Cianci, who is not among the creators involved in the lawsuit, was livestreaming outside the hearing to update viewers on proceedings.
She told the BBC that 65,000 people tuned into her TikTok Live. “The American people care about this issue,” she said. “They’re tuning in because they’re worried about losing something.”