Congress says the popular video app poses a looming threat to the nation’s security because of its Chinese owner. What the justices decide could determine if the app is shut down.

The Supreme Court signaled in oral arguments Friday that it may uphold the federal ban on TikTok, potentially leaving it up to President-elect Donald Trump to try and keep the app legal once he takes office — but the president-elect has limited options if the law is upheld, and any attempts to stop it could be challenged in court.

TikTok and ByteDance, as well as some users who post content on the app, have challenged a law that would compel the sale of the social media platform by Jan. 19 or ban it in the United States. The law was passed by Congress with strong bipartisan support last year and signed by outgoing Democratic President Joe Biden,