An image of the gun involved in the shooting of...

An image of the gun involved in the shooting of NYPD Officer Brian Moore presented is seen at a press conference in Manhattan on May 4, 2015. Credit: NYPD

If you oppose the passage of a federal law requiring background checks for gun buyers, you're endangering police officers and empowering cop killers . . . and you're not doing anything to protect the Second Amendment rights of law-abiding citizens.

In lieu of such a federal law, we have a hodgepodge of state rules, and in the South, where I grew up, they are often lax. And guns from those states, where weapons are easy for felons to buy, show up in states with tough guns laws, like New York, where they are tough to buy.

To take the worst offender as an example: At least 322 guns recovered during criminal probes from 2005 to 2014 on Long Island and at least 2,755 in the five boroughs have been traced to Georgia.

And illegal guns from Georgia have been linked to the killings of six New York City-area police officers, including Wenjian Liu, Rafael Ramos and Massapequa's Brian Moore of the NYPD.

The consistent argument against the point I'm making is that it doesn't matter to criminals whether you make guns harder to buy, because outlaws will arm themselves regardless. This ignores the power of that most conservative authority: the free market.

Lax gun laws drive down the price of illegal guns drastically. In Georgia, no ID or background check is required to buy a gun from a private, unlicensed seller, whether online or in person. And Georgia state law does not require reporting guns stolen, which means you can sell guns to an obvious cretin, and when the cretin or one of his customers kills someone, you can say, "That gun? Oh, it was stolen . . . did I not report that?"

So "straw buyers" can drive to Georgia (or South Carolina, or North Carolina, or plenty of other states) from New York, legally buy five handguns for $200 apiece and (illegally) sell them in New York to criminals for $400 or $600. The price is always much higher where the product is illegal. It's an easy way to make money.

If a federal law ended that safe method of illegal gun distribution by requiring background checks for legal purchases to ensure felons and the mentally ill couldn't buy guns, and setting a reasonable limit on how many guns a person could buy in a given period, it would not prevent all criminals from acquiring weapons, up north or down south. But it would drive the price of illegal guns through the roof, hugely increasing the black market premium paid by criminals. That's just what happens when supply is curtailed.

One or all of these men who killed our police officers might not have been able to afford illegal weapons if they were $2,000, as news reports say decent illegal handguns are in Great Britain, instead of the few hundred bucks they cost here. Making it harder for criminals and the insane to get guns with a federal law wouldn't drive up the price for law-abiding buyers, because they basically pay for the cost of manufacture and the cost of the seller doing business.

The right of law-abiding citizens to legally own guns, even handguns, is well established in this nation. The nixing by the Supreme Court of handgun bans in Chicago and the District of Columbia over the past few years reaffirmed that.

So when the National Rifle Association and its supporters fight federal laws demanding background checks for gun purchases and limits on how many guns people can buy in a specific period, it's important to understand what they're fighting for: it's not the right of law-abiding citizens to own guns, that's not under attack. It's the right of criminals and the mentally ill to kill cops like Liu, Ramos and Moore.

Lane Filler is a member of Newsday's editorial board.

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