For all of the decades of debate about what the Second Amendment means, it apparently took a Tucson gun store owner just a few weeks to discover the limits to the right to bear arms: people who support gun control aren't covered. Sorry, Mark Kelly. Your assault rifle purchase has been cancelled.

Earlier this month, Kelly, the astronaut husband of former Rep. Gabby Giffords, bought an AR-15-style rifle and a handgun at Diamondback Police Supply. Kelly did so to prove a point about how easy the weapons are to procure: he posted a photo of himself filling out paperwork on Facebook a few days later, noting that the required background check only took "a matter of minutes," and that it was "scary to think of people buying guns like these without a background check at a gun show or the Internet." Kelly also said he planned to turn the AR-15 over to Tucson police.

That provided the store owner an opening. On the day Kelly bought the weapon, Diamondback's owner, Doug MacKinlay, seemed content with the purchase. The Arizona Daily Star reported:

MacKinlay said Kelly never revealed to the store's staff why he was buying the guns and added that it would be wrong to refuse to sell a gun to someone because of their personal views.

"He is a U.S. citizen, an Arizona citizen and expressing his Second Amendment right to purchase and own a firearm," MacKinlay said.

MacKinlay expressed a similar sentiment in his own Facebook post on the sale. "To suggest that we should refuse a lawful sale to any qualified individual because we may disagree with the individuals political or personal views on a particular subject is wrong and is not a business practice that my company or our employees would ever engage in."

Because the rifle was used, Kelly couldn't take immediate possession of the weapon, instead having to wait for a review ensuring it hadn't been used to commit a crime. That delay allowed MacKinlay to change his mind about the sale — if not his company's stance on customers' political views. In another Facebook statement yesterday, MacKinlay writes:

While I support and respect Mark Kelly’s 2nd Amendment rights to purchase, possess, and use firearms in a safe and responsible manner, his recent statements to the media made it clear that his intent in purchasing the Sig Sauer M400 5.56mm rifle from us was for reasons other then for his personal use.

His argument is basically that Kelly was committing a "straw purchase" — buying the weapon for someone else. It's a bit of a stretch of the definition; what Kelly did is basically the same as buying a gun as a gift. (Increasing penalties on straw purchases are one component of the Senate's gun control package that deals with traffickers.) Instead of it going to Kelly, MacKinley indicated that the rifle would be given to the Arizona Tactical Officers Association to be raffled off, and that Diamondback would donate an amount equivalent to its cost to the NRA's child gun safety program.

Commenters on MacKinlay's post were enthusiastically supportive. "Gun control in action! Thank You! I guess it isn't all that easy to walk in and buy an 'assault weapon' after all," reads a typical response, here from David Bennett.

It's a response similar to what MacKinlay likely received after similar recent advocacy for gun rights. He was also interviewed by the Daily Star for a story about increased gun sales after the shooting as Newtown, suggesting that the holidays and shooting combined to increase sales. As did fear of new legislation. "I consider it absolute that we will see some kind of legislation come down the pike," MacKinlay told the paper. "I was concerned as soon as the elections were over." In another news article, MacKinlay indicated skepticism about a proposal to increase scrutiny on sales of rifles near the Mexican border, saying, "I don't consider that it's going to be effective at all." (MacKinlay was not quoted in an article last May reporting that a customer shot himself to death at his store.)

It's possible, if not likely, that MacKinlay's reversal was as purely a political move as Kelly's purchase. But — if the reaction he's gotten is any indication — he's also made a smart business decision. Diamondback Police Supply is an opponent of new gun regulations and open for business. At least as long as the customers are opponents of new gun regulations as well.