When the Supreme Court meets later today to discuss pending petitions for review, the justices’ conference calendar will include a pivotal Second Amendment case: Kolbe v. Hogan.

In Kolbe v. Hogan, the full Fourth Circuit Court of Appeals upheld Maryland’s ban of semiautomatic rifles and detachable ammunition magazines that exceed ten rounds. In doing so, the Fourth Circuit became the fourth federal appellate court to uphold the constitutionality of a ban on “assault” weapons and large-capacity magazines. The Second, Seventh, and District of Columbia circuits have previously upheld similar bans, and, to date, the Supreme Court has refused to enter the fray.

But Kolbe v. Hogan will likely force the justices’ hand. Here’s why.

Three Different Standards for Constitutionality

While the four circuit courts that have considered the constitutionality of bans on “assault” weapons and large-capacity magazines have all upheld the gun-control legislation, in doing so they have adopted three different standards for judging the constitutionality of the laws under the Second Amendment and the Supreme Court’s Heller decision.

The Second Circuit and the D.C. Circuit both concluded Second Amendment protections extend to semiautomatic rifles and large-capacity magazines. But, because banning such weapons and ammunition does “not seriously impact a person’s ability to defend himself in the home,” the appellate courts held that the appropriate question for them to consider is whether the government established a substantial relationship between the prohibition and an important state interest.

In the law, the “substantial relationship” with “an important state interest” standard is called “intermediate scrutiny.” The Second Circuit and D.C. Circuit then both concluded that the laws at issue satisfied intermediate scrutiny and thus upheld the bans.

Conversely, the Seventh Circuit in Friedman v. City of Highland Park crafted a different test, reasoning that, “instead of trying to decide what ‘level’ of scrutiny applies, and how it works,” it is more suitable “to ask whether a regulation bans weapons that were common at the time of ratification or those that have some reasonable relationship to the preservation or efficiency of a well-regulated militia, and whether law-abiding citizens retain adequate means of self-defense.” Applying that standard, in a split 2-1 decision, the Seventh Circuit upheld the Highland Park ban on semiautomatic weapons and large-capacity magazines.

Semiautomatics Are Bannable, Like Fully Automatics?

But rather than follow the lead of its sister circuits, the en banc court in Kolbe forged a third path: The majority opinion concluded “that the banned assault weapons and large-capacity magazines are not constitutionally protected arms.”

The Fourth Circuit reached this conclusion by first noting that the Heller Supreme Court recognized that the Second Amendment guarantee “extends only to certain types of weapons” and that “weapons that are most useful in military service – M-16 rifles and the like – may be banned” without infringing Second Amendment rights. The majority then concluded that the AR-15 and semiautomatic AK47 and other banned “assault” weapons and large-capacity magazines are “like” M-16 rifles, and therefore “they are among those arms that the Second Amendment does not shield.”

You don’t need to be well-versed in the intricacies of firearms to gasp at the Fourth Circuit’s equating of semi-automatic rifles with the fully-automatic M-16. This bizarre reasoning alone would justify the Supreme Court summarily vacating the Kolbe decision. In addition, as the brutal four-judge dissent in Kolbe made clear, the Fourth Circuit’s majority opinion is strikingly at odds with the Supreme Court’s decision in Heller.

Heller established as the dispositive question “whether the law bans types of firearms commonly used for a lawful purpose.” With AR-15 and AK-47-styled rifles accounting for approximately 20 percent of gun sales in the United States, those “assault” weapons definitely qualify as “commonly used” within the meaning of Heller.

Thomas: ‘Our Second Amendment Rights Are at Stake’

Nonetheless, as noted above, the Supreme Court has so far refused to clarify whether semiautomatic weapon and large-capacity ammunition bans withstand the scrutiny of Heller. The court’s hands-off approach earned justices the wrath of Justice Thomas, with whom Justice Scalia joined, in an opinion dissenting from the Supreme Court’s refusal to hear an appeal of the Friedman case out of the Seventh Circuit:

The Court’s refusal to review a decision that flouts two of our Second Amendment precedents stands in marked contrast to the Court’s willingness to summarily reverse courts that disregard our other constitutional decisions. There is no basis for a different result when our Second Amendment precedents are at stake. I would grant certiorari to prevent the Seventh Circuit from relegating the Second Amendment to a second-class right.

The Kolbe decision provides Justice Thomas another vehicle in which to push the Supreme Court to correct lower courts’ misunderstanding of the Second Amendment. Even if the other justices prefer to avoid the issue, by adopting yet a third standard for judging laws impacting the right to keep and bear arms, the Fourth Circuit has likely made a hands-off approach impossible: The Supreme Court will need to grant the petition for review to resolve the split in the circuits concerning the appropriate standard and to clarify the governing law.

But should the Supreme Court grant the petition for review, as I predict, gun-rights activists should temper any premature celebration. Public pressure to uphold “assault” weapon and high-capacity magazine bans will be great, and as Justice Thomas stressed: “If a broad ban on firearms can be upheld based on conjecture that the public might feel safer (while being no safer at all), then the Second Amendment guarantees nothing.”