The law—which prohibits U.S. app stores from hosting TikTok unless Chinese parent company ByteDance divests from it—is scheduled to take effect one day before Trump’s Jan. 2

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.

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,