Montana lawmakers voted 54-43 today to ban TikTok from operating in the state and forbid app stores from offering it for download. The legislation is likely to become law, which would make Montana the first state in the US to ban the popular social media platform—a move that could spark a constitutional battle and endanger digital rights.

People who already have TikTok on their devices would not be in violation of the law, which will now go to Greg Gianforte, Montana's Republican governor. The move comes after years of amorphous assertions from the United States government under two presidential administrations that TikTok, which has 150 million US users, is a threat to national security because its parent, ByteDance, is a Chinese company.

Gianforte is expected to sign the new bill into law, which would take effect on January 1, 2024. In December, he banned TikTok from Montana government devices, a step other states have taken in recent months as well. In announcing that ban, Gianforte said, “I also encourage Montanans to protect their personal data and stop using TikTok.”

A statewide ban is radically different from a government device embargo and general encouragement, though. It has implications for Montana residents’ speech and ability to hear speech—rights protected under the US First Amendment.

“We’re under no illusions that this is not going to get challenged,” Montana attorney general Austin Knudsen told The New York Times on Wednesday. "I think this is the next frontier in First Amendment jurisprudence that’s probably going to have to come from the US Supreme Court. And I think that’s probably where this is headed."

Soon after today's vote, TikTok condemned the bill on both First Amendment and logistical grounds.

“The bill's champions have admitted that they have no feasible plan for operationalizing this attempt to censor American voices and that the bill's constitutionality will be decided by the courts,” TikTok spokesperson Brooke Oberwetter said in a statement. “We will continue to fight for TikTok users and creators in Montana whose livelihoods and First Amendment rights are threatened by this egregious government overreach.”

A previous version of the bill would have required internet service providers to block connections to TikTok in Montana, a task that ISP representatives said wasn't doable. A trade association that represents companies that run mobile app stores, namely Google and Apple, also told the Montana legislature that it would be virtually impossible to halt downloads of TikTok in Montana.

Google declined to comment. Apple did not immediately return WIRED's request for comment.

Riana Pfefferkorn, a research scholar at the Stanford Internet Observatory, says Montana attorney general Knudsen's assertions about a “next frontier in First Amendment jurisprudence” are overblown, particularly given the AG's comments during the recent Times interview. In it, Knudsen specifically noted that his office was motivated to pursue a full TikTok ban after hearing protests from parents that TikTok posts included discussions of drug use, porn, and suicide.

“It's clearly unconstitutional,” Pfefferkorn says. “He admitted the purpose was to keep people from both saying and hearing legal speech. It’s an easy case."

More broadly, researchers have long warned that banning TikTok is incompatible with the democratic principles of the open internet. The US has consistently condemned platform blocks, content filtering, and internet shutdowns when other governments impose them on their citizens. These repressive digital tactics have been on the rise globally in recent years. Yet many US officials and lawmakers at both the state and federal levels have called for a TikTok ban.

“When ISPs and browser makers and tech companies are forced to develop technical methods to block access to networks and domains, it has very serious implications,” says Joseph Lorenzo Hall, a distinguished technologist at the Internet Society, a nonprofit that promotes an open internet. “It enables fragmentation or what we call the ‘splinternet.’ Communications platforms are a light switch in the dark. Marginalized communities use TikTok in ways that aren’t just ‘ha ha, let’s do a dance.’”

In March, TikTok CEO Shou Zi Chew testified before the House Energy and Commerce Committee in a hearing that largely devolved into anxious, Footloose-esque ruminations about child safety. Lawmakers raised concerns about TikTok that could be said of any social media platform and seemed to repeatedly, if unintentionally, make the case for comprehensive national privacy legislation in the US.

Meanwhile, even though Montana's ban will face legal challenges if passed, the very fact of its creation may embolden other states or even the federal government to consider paths to a TikTok ban, tipping off a chain reaction that could have profound impacts on freedom of digital expression in the US and around the world.

“It’s a maddening irony that American legislators’ idea for countering China is to act more like China, home of the Great Firewall that censors its citizens’ free access to the flow of information,” Stanford's Pfefferkorn says. “Banning a popular social media app, especially on the basis of speculative concerns, is directly contrary to the vision of a free and open internet that the US has long promulgated abroad as part of our commitment to democracy.”