The court handed down an unsigned opinion and there were no noted dissents.

The decision, which followed warnings from the Biden administration that the app posed a “grave” national security threat because of its ties to China, will allow the ban to start Sunday.

But there are a lot of lingering questions about how the ban would work in practice because there’s no precedent for the US government blocking a major social media platform. And how exactly the government would enforce it remains unclear.

In its opinion, the Supreme Court acknowledged that for 170 million Americans TikTok offers “a distinctive and expansive outlet for expression, means of engagement, and source of community.”

But the court said, Congress was focused on national security concerns and that, the court said, was a deciding factor in how it weighed the case.

“Congress has determined that divestiture is necessary to address its well-supported national security concerns regarding TikTok’s data collection practices and relationship with a foreign adversary,” the court wrote.

The ruling also puts the spotlight on President-elect on Donald Trump.

In the runup to the ban’s effective date, President Joe Biden’s administration signalled it would leave enforcement of the ban to Trump, who will be inaugurated on Monday.

Despite that, TikTok has said it may “go dark” when the ban takes effect.

A Biden administration official told CNN on Thursday that the outgoing president plans to leave it to Trump to enforce any ban.

“Our position on this has been clear: TikTok should continue to operate under American ownership,” a Biden administration official said.

“Given the timing of when it goes into effect over a holiday weekend a day before inauguration, it will be up to the next administration to implement.”

TikTok CEO Shou Chew is set to be seated on the dais, alongside other leading tech CEOs, at Trump’s inauguration — perhaps a sign of just how serious the incoming president is about trying to save the app.

And with some in Congress now suggesting that TikTok might need more time to find a buyer, Trump could find support in trying to push off the ban to a later date.

The law gives the president the option to extend the ban by 90 days, but triggering the extension requires evidence that parties working on purchasing have made significant progress, including binding legal agreements for such a deal — and TikTok’s parent company, ByteDance, hasn’t publicly updated its stance that the app is not for sale.