The court heard 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 are expected to rule quickly in the case, which pits national security concerns about China against the First Amendment’s protection of free speech.

TikTok has just ten days until it faces a possible ban in the US. If the Supreme Court declines to halt the law before January 19th, and TikTok isn’t spun off from its Chinese parent company ByteDance, companies like Apple and Google will be forced to stop maintaining the app in their app stores or letting it push updates.