Republicans proposing the repeal say they're not convinced the new requirements are improving public safety, and that the expanded background checks are infringing on the constitutional rights of law-abiding citizens.
Senate Democrats defeated the repeal bill Monday on a 3-2 party-line committee vote after dozens testified for and against the proposal in the Capitol's largest hearing room, which was packed with a couple of hundred people.
But the crowd didn't equal the size or the intensity of last year when gun rights supporters drove their honking cars around the Capitol in protest as lawmakers discussed a package of gun-control bills spearheaded by Democrats.
National Rifle Association lobbyist Daniel Carey called last year's law "unnecessary and unconstitutional." He argued the new law has shown evidence that it has curbed violent crime.
"Really, it only unnecessarily burdens law-abiding citizens," he said.
Democrats and supporters of the expanded background checks spent much of their time citing figures from the Colorado Bureau of Investigation, which found that 104 people with criminal records tried to buy guns but failed background checks during private transactions since the new requirements took effect July 1.
Among the crimes that resulted in denials were one homicide, six restraining orders and 16 assaults.
In all, 6,076 background checks have been conducted for private and online sales. That's a small percentage of the overall number of checks for the year, which stands at 389,604.
The rate of denial for firearms after a background check on private and online transactions is just under 2 percent, about the same as the overall rate of denial for all gun sales.
The new background check requirement was one of a handful of gun restrictions Democrats passed last session at great political cost. Another bill limited the size of ammunition magazines to 15 rounds. Republicans are also trying to repeal that law.
A pending federal lawsuit also seeks to overturn the new background checks and the magazine limits.
Two Democratic senators lost their seats through subsequent recall elections as a result of the gun restrictions, and a third resigned under pressure when a recall effort was underway.
Pueblo Republican Sen. George Rivera, who replaced one of two Democratic senators who were recalled, sponsored the bill to repeal the new background checks.
"When people are bent on committing mayhem they're going to do it, and the laws notwithstanding," Rivera said. He called the background-check expansion onerous to the majority of the population and said Pueblo voters "sent me here to deliver a message."
Supporters of the new laws say the measures were necessary in the aftermath of mass shootings at a suburban Denver movie theater and an elementary school in Connecticut.
"If only one person convicted of assault or domestic violence is prevented from getting a gun because of this law then our state is that much safer," said Jennifer Hope, leader of the Colorado chapter of Moms Demand Action for Gun Sense in America.
Some gun stores are refusing to do the background checks for private transfers, saying they're too costly. That's because in addition to the actual cost of the check, which is about $10, the new law says the gun shops can't charge a service fee of more than $10 for those private sales. However, some gun dealers says it costs them as much as $100 to do those checks.
"We've had a number of people come in, and we've just politely told them that we're not offering that service currently," said Richard Taylor, the manager at Aurora's Firing-Line.
Theresa Hoover's son, 18-year-old son AJ Boik, was among the 12 people killed the summer of 2012 in a suburban Denver movie theater during a midnight screening of "The Dark Knight Returns."
Hoover urged lawmakers to keep the expanded background checks intact, saying "we all know that it only takes one criminal with one gun to devastate a family or a community."
She told lawmakers that her son died in the arms of his fiancee after being shot in the head.
"He was 18 years old and just graduated high school and was going to go to college," Hoover said. "He was in movie. He was doing one of his favorite things with someone he loved in a place where he should've been safe."
Read the bill:
Senate Bill 94: http://goo.gl/sccIs4