This week, the House of Representatives is expected to vote on the Concealed Carry Reciprocity Act of 2017, the current incarnation of a proposal that has stood as the National Rifle Association’s top federal legislative priority for a decade. The bill would make a license to carry a concealed firearm issued by one state valid across the entire country, regardless of the vast differences that can exist between permitting standards. To grease its progress, the Republican House majority has combined the reciprocity measure with a pair of other gun bills, one of which is a version of a bipartisan effort to bolster the Federal Bureau of Investigation’s gun background check system.

Reciprocity has generated serious opposition from gun violence prevention activists, blue-state politicians, and law enforcement officials. One surprising source of criticism, however, is conservative legal scholars and pundits, many of whom believe the bill rests on a shaky constitutional foundation and will invite a court challenge should it pass into law.

“As drafted, the bill faces substantial constitutional objections,” law school professors Stephen Sachs, Randy Barnett, and William Baude wrote in a March letter to Representative Richard Hudson, a Republican from North Carolina who sponsored the bill. “This is a broad and unjustified assertion of federal power.”

Back in 2011, Representative Justin Amash, a conservative Republican from Michigan, called a nearly identical reciprocity bill “unconstitutional.”

It’s crucial to understand that the proposal to make an individual gun owner’s concealed-carry permit valid across the country is not grounded in the Second Amendment. While the NRA refers to reciprocity as “national right-to-carry,” courts have thus far not recognized such a right.

In fact, in District of Columbia vs. Heller, the Supreme Court opinion establishing an individual right to gun ownership, Justice Antonin Scalia noted that courts have upheld restrictions on concealed carry since the 19th century. More recent court challenges asserting that such a right exists, like one brought by a California gun owner against the strict permitting standards enforced by San Diego County, have failed.

To sell their idea, reciprocity proponents assert that concealed-carry licenses should be treated like driver’s licenses. But that concept overlooks a critical fact: states don’t recognize driver’s licenses because the federal government passed a law forcing them to, as the Concealed Carry Reciprocity Act would do with guns. Rather, states enter into a voluntary compact to allow visiting drivers to use their roads. Meanwhile, states refuse to recognize many other kinds of important licenses, like professional licenses for teachers or attorneys, choosing to impose their own standards on practitioners within their borders.

Because it can’t invoke the Second Amendment, the reciprocity act bases its constitutionality on the “commerce clause,” which grants Congress the right to regulate interstate commerce. The text of the bill specifically refers to guns that have “been shipped or transported in interstate or foreign commerce.”

That framing gives many conservatives pause. The commerce clause has been a bête noire for many Republican-affiliated jurists since at least the New Deal, when Democrats used it to assert vast new federal regulatory powers.

“It is perverse that conservatives, who have for decades railed against an expansive commerce clause jurisprudence, would suddenly cite the commerce clause to advance gun rights,” Josh Blackman, who teaches at the South Texas College of Law, wrote in a 2015 blog post.  Blackman is steeped in right-leaning legal thinking. He wrote a book about Obamacare’s alleged trampling on religious liberty.

The reciprocity bill uses the commerce clause in a way that another conservative observer regards as wildly expansive. “Carrying such an item, perhaps decades after it was purchased, cannot in itself possibly be seen as an act of commerce,” Robert VerBruggen, the managing editor of National Review, wrote in June. 

There is some precedent for using the commerce clause to regulate where gun owners may carry their weapons: In a stroke of  irony, the reciprocity bill actually uses the same language as the revised Gun Free School Zones Act. After the Supreme Court threw out the original 1990 law, Congress added commerce clause language, and the revised statute has since been upheld.

The problem with applying the commerce clause to concealed-gun permits, Blackman told me in an interview, is that its powers don’t operate on their own. Instead the commerce clause is typically used in conjunction with a separate clause that grants Congress the authority to pass laws “necessary and proper” to execute its authority.

A prominent example of why it’s necessary for legislation to meet the “necessary and proper” standard can be found in  the Supreme Court’s split-the-baby decision upholding the Affordable Care Act. In that case, five of the justices found that the key provision of the law, the individual mandate, was enforceable under Congress’s authority to levy taxes. But at the same, the court ruled that it was not “proper” to compel citizens to buy insurance, which meant that the insurance mandate could not be justified under the commerce clause, as the Obama administration had argued.

Similarly, Blackman said, courts may find it is not “proper” to compel states to cede sovereignty over the policing powers that are at stake when it comes to recognizing concealed gun permits.

Which cues up a second stroke of irony. Per Blackman, “It won’t be difficult for anti-Second Amendment liberals to cite the Obamacare decision,” in launching possible court challenges to national concealed carry reciprocity.

Most importantly, as Blackman has written, concealed carry reciprocity, “turns federalism on its head. Rather than states serving as laboratories, all states would be bound by the boldest experiment.”

To understand how reciprocity would upend state’s rights, consider how it would simultaneously undermine the laws of both liberal states like New York and ardently pro-gun parts of the country, like Texas.

To get a concealed-weapon license, New Yorkers must demonstrate a good reason for going about the world armed, like having received documented threats. Across the state line in Vermont, gun owners who want to carry concealed pistols don’t need a permit at all: Anyone who can legally own a gun can take it with them whenever they leave the house. The bill would force New York to abide by Vermont’s much more lax approach.

Texas, for its part, is one of 35 states that prohibit domestic abusers from carrying concealed guns. Alabama does not. Under reciprocity, Texas police couldn’t prohibit Alabamians convicted of beating their girlfriends from carrying concealed weapons in the state.

If the bill does make it to President Donald Trump’s desk, the issues that conservative legal experts have raised about concealed carry reciprocity would likely form the basis of lawsuits seeking to have the law thrown out, said Adam Skaggs of the Giffords Law Center to Prevent Gun Violence.

“There is no question that legal challenges would be filed very soon after the legislation became law,” he wrote in an email.