TikTok and the US government clashed in court Monday over the constitutionality of a looming US law that, if left in place, shutters the Chinese-owned social media app unless it sells to an American owner.

The law —the Protecting Americans from Foreign Adversary Controlled Applications Act—bars US foreign adversaries China, Russia, Iran and North Korea from controlling certain US mobile applications.

TikTok and a group of its users asked the US Court of Appeals in Washington, DC to block the government from enforcing the Act, which requires TikTok’s Chinese parent company, ByteDance, to either divest its US operations to a US company by January 19—or face a nationwide ban.

The matter, however decided, is expected to be challenged in a petition to the US Supreme Court.

According to TikTok and a group of content creators who use the platform, the law violates the US Constitution by singling them out and infringing on their protected speech.

“What it’s doing is taking away the rights of an American speaker,” TikTok’s lawyer, Andrew Pincus, said during a hearing before a three-judge panel.

Justice Department lawyer, Daniel Tenney, disagreed.

His view: the Act was a valid decision by Congress to protect Americans’ data from abuse by foreign adversaries, targeting only foreign “covert manipulation of content” that doesn't qualify as protected speech.

“If you call the covert manipulation of content ‘expression’...it is not expression by Americans, in America. It is expression by Chinese engineers, in China,” Tenney said.

The motivation for the law, he said, was national security and had “nothing to do” with protected speech—and that TikTok’s sale to a US entity would persevere expressive activity on the platform.

The judges, Chief Judge Sri Srinivasan, Circuit Judge Neomi Rao, and Senior Circuit Judge Douglas Ginsburg, pressed both sides on whether TikTok’s US entity, ultimately controlled by its Chinese parent ByteDance, is entitled to speech protection, and whether a strict or intermediate level of scrutiny should apply to evaluate the law’s constitutionality.

Tougher scrutiny is applied when certain types of speech restrictions are imposed on US citizens and US entities.

Circuit Judge Neomi Rao, a president Trump appointee, asked TikTok why the court should extend any Constitutional protections to TikTok when the US Supreme Court has held that no such right exists for foreign speakers outside the US.

“Does the First Amendment even apply?” Rao said.

TikTok's Pincus characterized both TikTok and its users as Constitutionally-protected speakers and argued that TikTok gained Constitutional protection by establishing its US arm, TikTok US.

Jeffrey Fisher, a lawyer for TikTok’s users, argued that the Act directly implicates his clients’ First Amendment rights by taking away their right to select a publisher of their choice.

“Once that speech is directed into the US, and certainly once that speech is in concert with other Americans, and indeed propagated by other Americans, the speech is not Chinese speech, it is American speech, that, at most, is curated by a foreign company,” Pincus said.

Senior Circuit Court Judge Douglas Ginsburg, a president Reagan appointee, shot back at TikTok’s contention that the law singled out the platform.

“That’s a rather blinkered view that the statute just singles out one company,” Ginsburg said, adding that TikTok happens to be an entity subject to the law after it engaged in two years of negotiations with the US government and failed to reach an agreement.

Chief Judge Sri Srinivasan, appointed by president Obama, expressed concern that content curated abroad by TikTok is still consumed by American recipients who are entitled to First Amendment protection.

“What you're doing is you're targeting curation,” he told Tenney, “...it’s just that the curation that's being targeted is happening abroad.”

But Tenney argued that the because law does not target TikTok users, the expressions they receive on the app are not automatically protected by the First Amendment.

Tenney said the law addresses a particular problem for the US in that the data collected by TikTok for its commercial purposes, is also valuable to the Chinese government.

That data, he said, includes users’ patterns, contacts, where they go, who they interact with, and what sorts of content interests them, and foreign adversaries use that information to recruit Americans as intelligence assets, or to cater messages that support their own national security.

Under Chinese law, the data can be used to compromise US security, he said, because TikTok must turn over its user data to Chinese officials if they demand it.

The judges' ruling could turn on the level of scrutiny applied in their review of the Act.

Judge Rao asked TikTok why the court would need to apply its toughest standard to TikTok's expressions, even if the platform were entitled to First Amendment rights as a US corporation.

Pincus reiterated TikTok's contention that it was signed out by the law and that in those cases strict scrutiny applies. He said in cases where such a foreign speaker's speech is restricted, US courts have, at most, required a label explaining the content's purported risk.

Alexis Keenan is a legal reporter for Yahoo Finance. Follow Alexis on X @alexiskweed.