Coloradans laid the path 10 years ago. Now it’s time for the nation to follow it: Close the gun show loophole.

The father of a Columbine High School student killed in the April 20, 1999, shootings has led the fight to close the gap. Last week, Tom Mauser, father of Daniel, received an additional boost in his fight when the Mayors Against Illegal Guns’ launched a nationwide ad campaign to push for the passage of national legislation that would do what Colorado already has done.

The loophole allows anyone to buy a gun from a private gun seller at a gun show without a background check.

The guns used at Columbine were obtained that way.

The gun used just last month to shoot two Pentagon police officers was bought at such a show.

Those are just a couple of high-profile instances of guns landing in the wrong hands and being used inappropriately.

A 2009 investigation by New York City found that 63 percent of private sellers at gun shows sold to a buyer who said he “probably couldn’t pass a background check.”

John Bedell, the Pentagon shooter, could not.

Closing the loophole is not about denying gun rights. It’s about holding all sellers to the same standards traditional retailers and sellers must uphold.

A bill pending in Congress, co-sponsored by Colorado Rep. Diana DeGette and Sen. Michael Bennet, would apply the law more evenly.

It’s common sense.