Protesters who cover their faces could spend more than a decade in prison under an anti-anti-fascist bill by House Republicans.

The “Unmasking Antifa Act,” introduced last month by Rep. Dan Donovan of New York, would impose harsh penalties on anyone who “injures, oppresses, threatens, or intimidates any person” while wearing a mask or disguise. The legislation, which could send people to prison for up to 15 years, mirrors controversial state laws originally designed at cracking down on the Ku Klux Klan. But unlike those state laws, Donovan’s bill is a direct shot at leftist protesters. And it might be unconstitutional, experts say.

“The thing I think is kind of funny is that the title is refers to ‘antifa,’” Ruthann Robson, a law professor at the City University of New York told The Daily Beast. “One issue there would be: is this law targeting a certain group of people?”

Robson is the author of Dressing Constitutionally: Hierarchy, Sexuality, and Democracy from Our Hairstyles to Our Shoes, which examines the intersection of law and constitutional rights, including anti-mask state laws.

“That would be a way to argue that it was unconstitutional,” she said. “Is it general, or just targeting this group? Because a law targeting some group’s expression would be more problematic. You could call it viewpoint discrimination. There could even be some equality arguments.”

Mark Bray, a Dartmouth College lecturer and the author of Antifa: The Anti-Fascist Handbook, which charts anti-fascism’s history, said politicians often speak too broadly when referring to the movement.

“Whenever I see politicians talking about antifa, the level of information they have is minimal,” he told The Daily Beast. “In a certain sense, they’re talking about what they perceive as leftists.”

The antifa movement, which originated from resistance to European fascism in the run-up to World War II, refers to leftist activists opposed to the far-right, racism, and often capitalism. Adherents might work with local anti-fascist organizations, but the movement is otherwise autonomous. But as the movement gained visibility around President Donald Trump’s election, it earned headlines in the conservative press, which sometimes erroneously refers to the movement as a unified entity, or a gang. The conservative media frequently calls for the “unmasking” anti-fascists.

Not all anti-fascists cover their faces, Bray noted.

“ Whenever I see politicians talking about antifa, the level of information they have is minimal. In a certain sense, they’re talking about what they perceive as leftists. ” — Mark Bray, Dartmouth College

“There are plenty who don’t,” he said. “Those who do [mask up] do it for pretty straight-forward reasons having to do with not wanting to be identified by the far-right, and not wanting to be identified by law enforcement. Certainly the importance of doing that has increased with the development of mass surveillance: with having more security cameras and smartphones. It’s difficult in this day and age to do anything politically in public without being identified as such.”

An anti-fascist organizer from New York (the home state of Donovan and the bill’s co-sponsor Rep. Peter King) traced masked protest back to the American Revolution.

“Protesters have always disguised themselves in order to mitigate state repression,” the organizer, who goes by the pseudonym Mollie Steimer told The Daily Beast. “For example, the Sons of Liberty disguised themselves [as Native Americans] when they went on to destroy property during the Boston Tea Party.”

Anti-fascists and fascists have recently engaged in doxxing campaigns against each other. After the text of the bill began circulating Monday night, members of the far-right took to Gab, a white supremacist-friendly social media site and urged their peers to support the bill.

Donovan’s bill would mean up to two years of additional prison time for people convicted of wearing a mask or disguise while damaging property, and up to 15 years in prison for masked activity that “injures, oppresses, threatens, or intimidates any person,” some of which might be unenforceable.

“‘Oppress’ doesn’t really have a legal meaning, so that would probably be subject to an unconstitutionally vague challenge,” Robson said.

But law enforcement has previously used broad laws to crack down on leftist and anti-fascist protesters. Outside Trump’s inauguration in Washington, D.C. last January, police arrested more than 200 demonstrators, journalists, legal observers, and bystanders en mass.

A superseding indictment against approximately 200 people (known as the “J20” defendants) accused them of conspiracy to riot, based on evidence as flimsy as the fact that some demonstrators wore black or masks. The case was finally dropped with no convictions last week, after a drawn-out legal battle in which federal prosecutors were revealed to have violated court rules by concealing and lying about alterations they’d made to a video by the right-wing media group Project Veritas. The video had been a key piece of evidence against the defendants, whom prosecutors described as antifa.

Anti-masking laws that once targeted the KKK have also been used to arrest anti-racist protesters at recent demonstrations.

In Charlottesville, Virginia last July, three activists were arrested for concealing their faces while protesting against a KKK rally. (The charges were later dropped.) The activists said they had used t-shirts to protect their faces when police started dousing the demonstration with tear gas. The following month, Klansmen would return to the city with a larger contingent of racists during the deadly Unite the Right rally. In Georgia this April, police arrested multiple people at gunpoint for wearing masks while protesting a public neo-Nazi rally.

Steimer, the New York anti-fascist organizer, viewed Donovan’s bill as part of an attack on the left that includes police surveillance of activist groups and police brutality during the Occupy movement.

“The point of these laws is always to protect the status quo of inequality and to use the power of the state to enforce compliance to this inequality,” Steimer said. “This particular law follows this same pattern: it wants to criminalize people fighting fascism, whether that be the kind of scum involved in torchlit marches in Charlottesville, or the ones who rip children away from their parents.”

But constitutional challenges to state anti-masking laws have previously proven difficult, Robson cautioned. Supreme Court Justice Sonia Sotomayor previously heard a KKK challenge on a New York anti-masking law when she was a circuit court judge. Sotomayor’s opinion “said the anti-masking law didn’t interfere with their expression because they could express their affinity for the KKK through other means like their robes and their signs,” Robson said.

Now the KKK might have an unlikely ally in Donovan’s bill, which targets their opponents

“I think this also needs to be situated in the context of the failure of the prosecution of the J20 trials, and the frustration certain politicians or certain state officials have with the inability to completely eliminate politics that are completely outside the ballot box, politics that are disruptive,” Bray said.

“Ultimately, I think this is a contestation over the potential for political anonymity: is that something that, in our future societies, will even be possible? And if we take resistance seriously, how important is that?”