According to Firearm Chronicles
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.