In Caldara v. City of Boulder, No. 18-1421, 2020 WL 1814596 (10th Cir. April 10, 2020), plaintiffs challenged the constitutionality of a local ordinance regulating the sale and possession of 
firearms. The federal district court abstained from exercising its jurisdiction. The Tenth Circuit affirmed this discretionary decision under Railroad Commission of Texas v. Pullman, 312 U.S. 496 (1941), concluding that the district court properly abstained and stayed the federal proceedings pending resolution of important state-law issues.
Boulder’s Firearms Ordinance
In May 2018, the Boulder City Council passed Ordinance 8245, which prohibits the sale or possession of assault weapons and large-capacity ammunition magazines within the city. The Ordinance also raised the legal age for possession of any firearm from 18 to 21.
