The Maine Legislature should be applauded for taking a small but significant step Wednesday. It stood up to the National Rifle Association.

Both houses passed a bill to make it harder for someone to buy a gun if that person is legally prohibited from possessing one, either because of a history of domestic violence assault or felony convictions or involuntary commitment to a mental institution.

Under current law, those people would be denied a gun by a licensed firearms dealer but not necessarily by a private seller, because they’re not required to conduct background checks. An estimated 40 percent of gun sales are private transactions, so this is more than just a small loophole.

Crafted by Rep. Mark Dion, D-Portland, a former police officer and sheriff, the bill came up with a novel way to close the gap. His bill still makes background checks optional in private sales, but it would fine a seller $500 if he skipped the check and sold a gun to a person who is not allowed to buy one. After a first offense, the penalties would increase, eventually rising to misdemeanor crimes.

This is a very reasonable change to the law, and it could make background checks much more common. It doesn’t affect anyone who is legally able to own guns now. It doesn’t interfere with private sales between relatives and family members. And it’s not a controversial notion to most of the public, according to polls that show overwhelming support for toughening the background check law.

All it would do is place some responsibility on sellers to know who they are dealing with.

That didn’t stop the NRA from trying to kill the bill with an action alert to Maine members over the weekend. It encouraged members to call their senators and representatives and get them to vote “no.” That’s the kind of tactic that has worked many times in the past, and almost worked this time. The Senate passed a watered-down version of the background check bill Monday, but came around Wednesday to the stronger House version.

What legislators passed could break a logjam on the background check issue that has stifled progress around the nation. Under this law, a seller who doesn’t know his buyer skips a background check at his own risk. Many sellers will decide that when dealing with a stranger, it’s not too much trouble after all to go to a licensed dealer and finish the sale with an instant check.

Passing these bills took tough votes by lawmakers (all Democrats and independents) who were aware of the gun lobby’s clout. They did the right thing and stood up to the pressure. Gov. LePage should do so, too, and sign this bill into law.