The Supreme Court seemed likely to uphold a law that would ban TikTok in the United States beginning Jan. 19 unless the popular social media program is sold by its China-based parent company. Hearing arguments in a momentous clash of free speech and national security concerns,

The court is hearing oral arguments on TikTok’s bid to block a law that would lead to its ban in the U.S. starting Jan. 19 if it isn’t sold by its Chinese owner.

The justices, who asked tough questions of both sides, showed skepticism toward arguments by lawyers for TikTok and its users.