From Associated Press - In 2018, Boulder, Colorado, voted to ban assault weapons. The law was then overturned on March 12, 2021, just 10 days before Monday's mass shooting that killed ten people. The city's law was blocked in court as a result of a lawsuit that was backed by the National Rifle Association, ruling that Colorado state law that prohibits local officials from making their own gun laws.
Investigators determined that the suspect behind Monday's mass shooting in Boulder purchased his assault rifle on March 16, 2021, just four days after the 2018 law was overturned.
Since the 1980s, most states have passed similar preemption laws pertaining specifically to gun rights to allow states to be consistent in firearm sales and enforcement. The goal in such preemption laws is to avoid confusion among law-abiding gun owners that may occur if gun rights were to fluctuate from one city to another within the same state.
Image from Associated Press