One bill expands background checks on firearm purchases, and the other limits ammunition magazines to 15 rounds. The 15-round magazine limit would make Colorado the first state outside the East Coast to ratchet back gun rights after last year’s shootings in Aurora, Colo., and Newtown, Conn.

Colorado’s gun-control debates have been closely watched because of the state’s gun-loving frontier heritage and painful history of mass shootings, most recently last summer’s movie theater shooting that killed 12.

The sheriff said he “won’t bother enforcing” the laws because it would be impossible for officers to keep track of how the requirements are being met by gun owners — and he and other sheriffs are considering suing the state to block the measures if they are signed into law.

Cooke said the bill passed Friday requiring a $10 background check to legally transfer a gun wouldn’t keep firearms out of the hands of those who use them for violence.