The law also gives the president the ability to grant a 90-day delay in its implementation if a sale is in progress.

The case pits the First Amendment's right to free speech against what the federal government and lawmakers say are threats to national security posed by TikTok. The Supreme Court moved with extraordinary speed in considering the case, agreeing to take up the dispute just two days after lawyers for the platform sought its intervention on an emergency basis.

Patrick Toomey, the deputy director of ACLU's National Security Project, said the government has not supported its claims against TikTok with concrete public evidence. The ACLU has urged the Supreme Court to block the ban in a friend-of-the-court brief.

"The government can't impose this type of total ban unless it's the only way to prevent extremely serious and imminent harm to national security," Toomey told CBS News. "That means not just gesturing at the possibility that these types of harms could come from exploitation of TikTok, but providing evidence that either those harms are ongoing and widespread or are imminent, and we haven't seen that kind of evidence.

The question before the court is whether the law targeting TikTok violates the First Amendment. Here are the issues to be decided:

The Protecting Americans from Foreign Adversary Controlled Applications Act makes it unlawful for third-party service providers like Google or Apple to "distribute, maintain or update" an app controlled by a foreign adversary by providing certain services, such as offering it in app stores.

Under the law, any app operated by ByteDance, TikTok, or its subsidiaries is considered a "foreign adversary controlled application." The designation also covers apps operated by a "covered company" controlled by a foreign adversary — China, Russia, North Korea or Iran.

The prohibitions are set to take effect 270 days after the law was enacted, on Jan. 19. Under the law, TikTok can remain available, however, if it divests from ByteDance. The measure also allows the president to grant a single, 90-day extension if a sale is underway.

In a brief laying out its arguments to the Supreme Court, the U.S. government said the vast amount of information TikTok collects on its users could be wielded by the Chinese government for "espionage or blackmail" purposes or to "advance its geopolitical interests" by "sowing discord and disinformation during a crisis."

"In response to those grave national-security threats, Congress did not impose any restriction on speech, much less one based on viewpoint or content. Instead, Congress restricted only foreign adversary control: TikTok may continue operating in the United States and presenting the same content from the same users in the same manner if its current owner executes a divestiture that frees the platform from the [People's Republic of China's] control," the Justice Department said.

Lawyers for TikTok have argued that shuttering the app in the U.S. will silence not only its speech, but also that of the 170 million Americans who regularly use it. In its filing, lawyers for the platform called the potential shutdown "unprecedented" and said the government's justification is "at war with the First Amendment."

Additionally, TikTok has argued that divesture from ByteDance is not possible, and the parent company said in April that it will not sell the platform.

Jennifer Safstrom, who directs the Stanton Foundation First Amendment Clinic at Vanderbilt Law School, said TikTok may have more of an uphill battle in making its case because "one of the strengths of the government's position is that the executive and legislative branches are given a lot of deference with respect to national security."

"So there's often a hesitancy for courts to second-guess the political branches on those kinds of national security questions," Safstrom told CBS News.

TikTok won't disappear from Americans' phones on Jan. 19 if the law takes effect. But, users would not be able to update the app and those who don't already have it would not be able to download it.