The First Amendment has so far played only a bit part in the debate about banning TikTok. This may change. If the U.S. government tries to shut down this major communications platform, the First Amendment will certainly have something to say about it.

Perhaps the reason First Amendment rights haven’t received more attention in this debate already is that TikTok is a subsidiary of ByteDance, a Chinese corporation that doesn’t have constitutional free speech rights to assert. But if we set aside the question of TikTok’s rights, the platform’s users include more than 150 million Americans, as TikTok’s chief executive testified at a contentious congressional hearing on Thursday. TikTok’s American users are indisputably exercising First Amendment rights when they post and consume content on the platform.

Six years ago, in Packingham v. North Carolina, the Supreme Court struck down a law that prohibited convicted sex offenders from using social media, reasoning that these websites had become “integral to the fabric of our modern society and culture.”

A half century before that, the Supreme Court decided a series of cases recognizing that the First Amendment protects not only the right to speak but also the right to receive information, including the right to receive information and ideas from abroad. In one of those cases, Lamont v. Postmaster General, the court invalidated a federal law that barred Americans from receiving “communist political propaganda” from foreign countries unless they specifically asked the Postal Service to deliver it. The court held that the law was an impermissible attempt “to control the flow of ideas to the public.”

So there’s really no question that government action whose effect would be to bar Americans from using a foreign communications platform would implicate the First Amendment. That’s exactly what one federal court held two years ago when it blocked President Donald Trump’s attempt to ban WeChat, the Chinese messaging app.

Of course, to say that a ban on TikTok would implicate the First Amendment is not to say that it would violate it. But a ban would have to satisfy First Amendment scrutiny to survive a constitutional challenge.

Indeed, there’s a strong argument that the government would have to satisfy the most stringent form of First Amendment review because the ban would operate as a prior restraint on the speech of TikTok’s would-be users. At the very least, the government would have to show that the ban is substantially related to important governmental interests.

The principal interests the government has invoked thus far involve protecting Americans’ data and depriving the Chinese government of a tool that could be used to spread disinformation. Even if we assume that these are important interests (the first plainly is; the second raises more difficult questions, as the Lamont case shows), it seems doubtful that the U.S. government would be able to establish that a categorical ban is tailored to them.

For one thing, the Chinese government can obtain private data about Americans without relying on TikTok. It can simply purchase the data from data brokers, as Glenn Gerstell, a former National Security Agency general counsel, explained a few weeks ago in a Times Opinion guest essay.

Also, as many digital rights advocates have pointed out, the federal government could protect Americans’ privacy much more effectively (and without the necessity of a categorical ban on a communications platform used by millions of Americans) by enacting comprehensive privacy regulation. As to fears relating to disinformation, the U.S. government has not pointed to evidence that the Chinese government has forced TikTok to align its algorithm with the imperatives of the country’s disinformation efforts. Given all of this, it’s difficult to see how a ban could survive First Amendment review. A broad coalition of free speech organizations—including PEN American Center, the Center for Democracy and Technology and the Knight First Amendment Institute, which I direct—made essentially this observation in a letter sent to Congress before Thursday’s hearing.

None of this analysis changes simply because the government says it is acting for national security reasons. The Supreme Court and lower courts have held repeatedly that the mere invocation of national security is insufficient to justify the suppression of First Amendment rights. In court, the government will have to introduce evidence that the threats it is addressing are real, not merely conjectural, and that the proposed ban would address those threats. The evidence assembled so far is not likely to be sufficient.

All of this will no doubt be frustrating to some policymakers, including to some who are commendably focused on the very real risks that social media companies’ practices pose to Americans’ privacy and security. But the legitimacy of our democracy depends on the free trade of information and ideas, including across international borders. Except in the most extreme circumstances, citizens should be able to engage freely with the communications platforms of their choice.

Perhaps there are contexts in which a ban on a social media platform could be reconciled with democratic values. It’s conceivable that the U.S. government will eventually be able to establish the necessity of a ban on TikTok, even if it hasn’t done so yet. But the First Amendment would require the government to carry a heavy burden of justification. This is an important feature of our system and not a bug.