A federal challenge to Boulder, Colorado’s ban on so-called assault weapons is on hold until the state Supreme Court weighs in on the legality of the local ordinance, thanks to a decision by the 10th Circuit Court of Appeals. The case was brought by a number of plaintiffs, including Independence Institute president Jon Caldara, after the city approved a ban on the possession of semi-automatic long guns in May of 2018, requiring existing gun owners to either remove any banned firearms from the city limits or turn them over to police, unless they “certify” their firearms with the city.

According to Colorado Politics, the 10th Circuit says that they won’t rule on the legality of the ordinance in question until the state Supreme Court decides if Boulder’s ordinance violates the state’s firearm preemption law.

Writing for the three-member appeals panel, senior circuit Judge Stephanie K. Seymour noted that an abstention is appropriate in cases where state law is unclear, as long as the decision is not arbitrary or unreasonable. “Both sides agree that the Boulder City Ordinance conflicts with Colorado statutes,” Seymour wrote. The question was whether the ordinance pertains to state matters, local matters under the jurisdiction of home rule, or a mixture of both. The appeals court found only one similar case, in which state Supreme Court justices split evenly on the question of whether Denver’s gun laws were permissible under home rule authority. In that instance, a lower court found that several provisions in the laws were entirely local in nature. Pointing to the lack of a Supreme Court majority on the matter as “not only uncertain but also potentially decisive,” Seymour referenced a 1941 court case out of Texas that produced a three-prong test for whether a federal court should hold off on deciding cases with state law implications.

The Mountain States Legal Foundation, which helped bring the case against the city of Boulder, has argued that the city’s ordinance violates not only the Second Amendment rights of residents, but also runs afoul of the state constitution and several state statutes as well.

The foundation asks two key legal questions regarding whether a municipality “can undermine the exercise of fundamental and unalienable rights and ignore the U.S. Constitution and controlling Supreme Court precedent?” Additionally they question if the city can legally “ignore its state constitution and state law by infringing upon and criminalizing an individual’s unalienable and natural right to self-defense, and the right to keep and bear arms?” City Ordinance 8245 banned the sale and possession of guns in the city defined as assault weapons in addition to bump stock devices and large magazines, and banned the sale and possession of weapons to anyone under age 21. Gun owners of such magazines had until July 15, 2018, to either sell or dispose of these items. The ordinance includes a grandfather clause that permits owners of these firearms to keep them in their possession if they receive a certificate from the local sheriff’s office proving their ownership and certifying their firearms. The law also bans them from openly carrying their rifles and shotguns. “My hope is that we will see more bans at the state level and one day at the federal level so these weapons will no longer be available,” City Councilman Aaron Brockett said after the ordinance passed.

The decision by the 10th Circuit Court of Appeals doesn’t mean that the lawsuit is over, but any movement in the federal case is on hold until Colorado’s Supreme Court weighs in on the legality of the Boulder ordinance. When that decision might come down is anyone’s guess, but in the meantime the gun ban remains in place, though it’s unclear how many residents have complied with the order to “certify” any semi-automatic long gun that is still possessed inside the city limits.