Democratic presidential candidate Joe Biden has done something unprecedented with his pick of Sen. Kamala Harris (D., Calif.) as his running mate: put a candidate on the presidential ticket who publicly supports gun confiscation.

During her failed primary campaign, Harris was one of only a handful of candidates to explicitly advocate for the confiscation of what she estimated to be tens of millions of legally owned firearms.

“We have to have a buyback program and I support a mandatory gun buyback program,” she said during an October policy forum hosted by the gun-control group March for Our Lives. “It’s got to be smart. We’ve got to do it the right way but there are five million [assault weapons] at least, some estimate as many as 10 million, and we’re going to have to have smart public policy that’s about taking those off the streets but doing it the right way.”

While Hillary Clinton advocated for a sales ban and even the reversal of the Supreme Court precedent overturning Washington, D.C.’s total ban on handgun ownership during her 2016 campaign, she never expressed support for any form of direct firearms confiscation. And though Joe Biden has advocated for even more stringent gun-control policies than Clinton—including a ban on all guns without “smart” features—he told CNN’s Anderson Cooper last year there is “no legal way” to confiscate guns Americans already own.

The Biden campaign did not immediately respond to a request for comment.

The addition of Harris moves the Biden campaign further to the left on gun control—beyond any other major party campaign in recent history. Gun-rights groups argue it may also damage the perception Joe Biden has cultivated as a more moderate Democrat.

“I think you’re dealing with a guy who’s got a complete and total anti-gun platform,” Jason Ouimet, head of the NRA’s political action committee, told the Washington Free Beacon in a recent interview. “And for that little bit of moderate that he wanted to purport, I think that went out the window.”

Mark Oliva, a spokesman for the National Shooting Sports Foundation, said Harris’s track record in Congress and on the campaign trail indicates she would push Biden even further to the left on the issue.

“During her short-lived presidential campaign, she demanded gun-control legislation within 100 days and threatened executive action if Congress didn’t deliver,” Oliva told the Free Beacon. “Senator Harris was clear when she said gun control would be an administration priority. Her platform included entertaining forced confiscation of lawfully owned semiautomatic rifles, redefining ‘sporting purpose’ for lawful firearm possession, criminalizing private firearm transfers and repealing the Protection of Lawful Commerce in Arms Act. In fact, she supports politicizing the Department of Justice and using the weight of the federal government to harass a constitutionally protected industry in a series of frivolous lawsuits to bankrupt manufacturers.”

Oliva called the pick a danger to gun owners.

“Joe Biden’s selection of Senator Kamala Harris as his running mate makes this ticket the most serious threat to American Second Amendment rights ever faced in a presidential election,” he said.

Gun-control groups, on the other hand, cheered Biden’s decision to name Harris his vice-presidential nominee. Giffords, the gun-control group headed by former congresswoman Gabby Giffords, emphasized Harris’s support for expanding background checks to private sales in a celebratory email to its donors and didn’t mention her support for confiscation.

“Joe Biden just announced his pick for Vice President and we are so thrilled to have Senator Kamala Harris join the fight to defeat Trump in November,” the group said in an email to supporters. “Like Joe Biden, Kamala Harris is a gun safety champion with a proven record of fighting the NRA and standing up for common sense. They will work tirelessly together to pass universal background checks and make every community safer from gun violence.”

Kris Brown, president of the gun-control group Brady United, described the pick as “a game changer for gun violence prevention” in an email to the group’s donors. She said Biden and Harris would pass gun-control measures like expanding and better funding the background check system, a ban on so-called ghost guns, and a ban on the sale of so-called assault weapons, but also did not mention Harris’s support for gun confiscation.

“By choosing Harris, Biden takes a bold stance,” Brown said in the email. “He proves he understands a fundamental problem our country is facing: gun violence. And with two gun violence prevention champions on the ticket, we can finally overcome the NRA, Donald Trump, and Mitch McConnell.”

Oliva sees Biden’s pick of Harris in a very different light.

“Senator Harris is a willing partner with Joe Biden to reinstate the failed ban on modern sporting rifles,” he told the Free Beacon. “His selection of Senator Harris as his running mate suggests he’s comfortable with setting aside fundamental American rights.”