State attorneys defended Colorado’s new gun restrictions Monday against a lawsuit to overturn them, saying the laws balance Second Amendment rights with public-safety concerns.

But attorney Richard Westfall, who is representing gun-rights advocates, says the laws are based on emotion rather than data that prove their effectiveness. He argues that the laws violate the Second Amendment right to bear arms.

The comments came Monday in Denver federal court during opening arguments of a two-week trial. The laws in question, which took effect July 1, limit the size of ammunition magazines to 15 rounds and expand background checks to firearm sales online and through private sellers.

Deputy Attorney General Matthew Grove noted the laws were a response to mass shootings at the Century Aurora 16 theater and Connecticut’s Sandy Hook Elementary School.

The first witness was Robert Hewson, executive director of nonprofit Colorado Youth Outdoors, which conducts outdoor programs that include trap shooting and gun safety for parents, mentors and teens.

The organization occasionally transfers guns to users of its programs so that they can participate in guided hunting trips, Hewson said, or for other reasons outside its property.

Hewson said the law, which requires background checks on those involved in gun loans that last longer than 72 hours, put the organization’s program in jeopardy.

Exemptions allow a person to give a gun to any family member without undergoing a background check, to loan a gun to a friend for up to 72 hours, or to let someone use their gun while at a shooting range or while hunting.

But CYO depends on the Maverick Shoot, a yearly shooting fundraising competition that brings in more than half of its $400,000 budget, Hewson said.

The organization doesn’t have enough guns for all participants and must borrow some. Typically, the nonprofit gets the weapons from other organizations a week or so before the May event so that those conducting it have time to make sure the guns are clean and safe.

They take another week or so after the three-day event to ensure the guns are returned in good condition, Hewson said.

The 72-hour limit on transferring the guns without a background check puts the organization in a bad spot, he said. “It is a very threatening and challenging position we are in.”

Tom McGhee: 303-954-1671, tmcghee@denverpost.com or twitter.com/dpmcghee