The U.S. Supreme Court decided Wednesday (Dec. 18) to hear TikTok and its Chinese parent company ByteDance’s appeal to block a law that seeks to force the sale of the short video app by Jan. 19 or it will be banned on national security grounds.

The justices did not immediately act on an emergency request by TikTok and ByteDance, as well as some users who post content on the social media platform, for an injunction to stop the impending ban, instead choosing to hear arguments on the matter on Jan. 10.

The challengers are appealing a lower court ruling upholding the law. About 170 million Americans use TikTok.

The U.S. Congress passed the bill in April and Democratic President Joe Biden signed it into law. The Justice Department has said that as a Chinese company, TikTok poses a “substantial national security threat” because it has access to a large amount of U.S. users’ data, from location to private messages, and is able to secretly manipulate what Americans view on the app. TikTok has said it does not pose an imminent threat to U.S. security.

TikTok and ByteDance asked the Supreme Court on Dec. 16 to suspend the law, which they said violated the First Amendment’s protection of free speech.

TikTok said Wednesday it was pleased the court would take the case. “We are confident the court will rule that the ban on TikTok is unconstitutional so that the more than 170 million Americans on our platform can continue to exercise their free speech rights,” the company said.

The companies said even a one-month shutdown would cost TikTok about a third of its U.S. users and undermine its ability to attract advertisers and recruit content creators and employees.

The U.S. Court of Appeals for the District of Columbia Circuit in Washington on Dec. 6 rejected the companies’ First Amendment arguments.

TikTok and ByteDance said in their filing to the Supreme Court that “if Americans choose to continue viewing content on TikTok knowingly, after fully understanding the alleged risks of ‘hidden’ content manipulation, the First Amendment gives them the right to make that choice free from government scrutiny.”

Senate Republican leader Mitch McConnell urged the court to reject any delay in a brief filed with the Supreme Court on Wednesday, likening TikTok to a hard-hearted criminal.

A U.S. ban on TikTok would make the company much less valuable to ByteDance and its investors and hurt businesses that rely on TikTok to drive sales.

Republican President-elect Donald Trump tried unsuccessfully to ban TikTok during his first term in the White House in 2020. He reversed course and pledged during this year’s presidential campaign to work to save TikTok. Trump said on December 16 that he had “a warm feeling for TikTok” and would “watch” the matter.

Trump will be inaugurated on January 20, the day after the legal deadline for TikTok.

“The First Amendment exists to protect free speech in the United States. Here, the government’s actions are designed solely to protect that freedom from a foreign adversary and to limit that adversary’s ability to collect data on the American people,” the D.C. Circuit Court of Appeals wrote in its ruling.

TikTok denies that it has or will share U.S. user data, accusing U.S. lawmakers of raising speculative concerns in the lawsuit. It called the ban “a radical departure from the American tradition of advocating for an open internet.”

The dispute comes as trade tensions between the world’s two largest economies are rising. It comes after the Biden administration imposed new restrictions on China’s chip industry, and China retaliated by banning exports of metals gallium, germanium and antimony used to make high-tech microchips to the United States.

The U.S. law would prohibit certain services from being provided to TikTok and other apps controlled by foreign adversaries, including through app stores such as Apple and Alphabet’s Google, effectively blocking TikTok from continued use in the United States unless ByteDance divests TikTok by a deadline.

An unhindered ban could open the door to future crackdowns on other foreign-owned apps. Trump also tried to ban WeChat, owned by Chinese company Tencent, in 2020, but was blocked by the courts.