According to the National Rifle Association, background checks of gun buyers can never be universal because criminals would never submit to them.

But several recent cases in Maine show how legal guns can easily be acquired by criminals who could not pass a background check because of the haphazard regulation system that is as bad as no regulation at all.

According to federal law, felons are banned from owning firearms. So are people convicted of a misdemeanor charge of domestic violence assault. So are those who have been involuntarily committed to a hospital as a result of mental illness.

That’s why gun buyers are supposed to go through instant background checks when they do business with a licensed firearm dealer. But that requirement is optional when they go to an unlicensed dealer. It’s called the “gun show loophole” because that’s one place a stranger can sell a gun to another stranger without any background check. But it could be called the “Uncle Henry’s exemption” in Maine, because the popular classified circular advertises scores of guns for sale by private sellers who don’t have to look into the buyers’ backgrounds.

A Feb. 10 story by Kevin Miller (“Many sales of firearms in Maine fall under the radar“) outlines three cases in which guns moved into criminals’ hands using the private sales loophole. In one case, a Portland man with a felony history bought a handgun that was advertised in Uncle Henry’s. He sold the gun to a contact in New York. The gun was used in a shootout with New York City police.

In another case, Portland police know that a gun was used in two homicides in the city, one unsolved. The gun was sold by its original owner at a gun show. There was no background check and there is no record of the sale.

In yet another case, a Boston man was sentenced to 17 years in prison for running a weapons supply operation for a gang, using guns sold privately in Maine.

These cases expose the weakness of the NRA’s argument. It’s true that criminals won’t submit to a background check — they don’t have to. As long as there is a legal no-background-check market in at least one state, they can skirt the law and acquire firearms whenever they need them. Cracking down on background checks does not infringe on the rights of legal gun owners, but it does make life more difficult for criminals. It may not make it impossible for a felon to get hold of a gun to use in a crime, but closing the private sale loophole would make guns harder to get and there may be fewer of them around on the black market.

If gun owners can’t live with background checks in 100 percent of sales, maybe they would prefer being held liable for crimes committed using guns they sold without a check. Under the current system, it’s too easy for guns find their way into the wrong hands and for no one to take responsibility.