Colorado Gov. Jared Polis signed a bill Friday banning firearms that are assembled at home or 3D-printed without serial numbers, weapons that allowed owners to evade background checks and impede law enforcement's ability to track a gun's origins in an investigation.
The new law is the latest in a slew of gun control measures signed by Polis this year. The state joins 11 others, including California, New York and Nevada, in regulating the so-called ghost guns, which have been linked to high-profile mass shootings across the U.S.
