STORY: The fate of the popular video-sharing mobile app TikTok fell before the U.S. Supreme Court on Friday.

TikTok, and its Chinese parent company Bytedance, appealed to the justices over a law that orders Bytedance to sell off TikTok in the next nine days, or see it banned in the U.S.

The case pits what TikTok says are free speech rights against what Congress and the White House have called national security concerns.

Here's TikTok attorney Noel Francisco, at oral arguments on Friday:

"Under the Act, one of America's most popular speech platforms will shut down in nine days."

Francisco said the law would set a dangerous precedent.

"The government's real target, rather, is the speech itself. It's fear that Americans, even if fully informed, could be persuaded by Chinese misinformation. That, however, is a decision that the First Amendment leaves to the people."

But the justices appeared skeptical. Here's an exchange between associate justice Clarence Thomas and the TikTok attorney:

THOMAS: "Exactly what is TikTok speech here?"

FRANCISCO: "TikTok, Your Honor. Uses an algorithm that, in its view, reflects the best mix of content. What the act does is it says TikTok cannot do that unless ByteDance executes a qualified divestiture. That's a direct burden on TikTok speech."

THOMAS: "You're converting the restriction on ByteDance's ownership of the algorithm and the company into a restriction on TikTok speech. So why can't we simply look at it as a restriction on ByteDance?"

The Biden administration claims that Chinese government control of TikTok poses a grave threat to American national security.

It maintains that TikTok's immense data set on its American users and their non-user contacts gives China a powerful tool for harassment, recruitment and espionage.

Chief Justice John Roberts pressed this point in an exchange with TikTok's lawyer, Francisco:

ROBERTS: "So are we supposed to ignore the fact that the ultimate parent is, in fact, subject to doing intelligence work for the Chinese government? "

FRANCISCO: "Well, Your Honor, I don't think you are supposed to ignore that at all. But I also don't think that it changes the analysis."

ROBERTS: "As I said, you began by saying this is a US company operating in the United States. And it seems to me that you're ignoring the major concern here of Congress, which was Chinese manipulation of the content and acquisition and harvesting of the content."

TikTok has asked the justices to either strike down the law or put its implementation on hold while they consider the merits.

And the firm has pointed to changing political winds in the U.S. as president-elect Donald Trump has said he opposes the legislation.

He's said he would try and find a political solution with the Chinese government.

But he doesn't take office until January 20, a day after the law goes into effect.