A TikTok ban might be one step closer to reality even if there are still some lingering doubts about whether a federal law will really go into effect on January 19.

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 lawyer for TikTok and its Chinese parent company ByteDance offered a warning during Supreme Court arguments over a law that would compel the sale of the short-video app or ban it in the United States: If Congress could do this to TikTok,