Arizona cities are going into the gun-selling business. Under a new law signed by Governor Jan Brewer yesterday, no weapon collected during a buyback program can be destroyed, meaning cities will need to either hoard or sell them. This is not usually how such programs work.

The goal of gun buybacks is to encourage criminals to turn in weapons that would otherwise be used in crimes in order to collect money (or, nowadays, a gift card). Those weapons are then usually checked to see if they were used in a crime or stolen or, if they're clean, destroyed. In Seattle, guns are recycled (naturally). In Indiana, guns are snapped in half. In Marin County, California, they are melted.

There's not a lot of evidence that gun buyback programs do much good to curb gun violence. While recent buybacks have turned up assault weapons and rocket launchers, most of the weapons collected aren't used by hardened criminals. Instead, they come from people who have old rifles or handguns around the house — often non-functioning ones — that they find less valuable than those gift cards. NPR's Scott Simon spoke with the chief of police in Santa Fe in January.

SIMON: Do you expect any real criminals to turn in their guns?

RAEL: Well, in reality, probably not. Anyone who is serious about stealing a weapon, and using it in a criminal act, isn't likely to turn it in. But we do anticipate that there will be some weapons turned in by members of the general public who have either inherited weapons, or are concerned about leaving weapons in their homes - loaded or unloaded - and just feel they no longer have any use for them. … [T]he other side of the equation is, if you look at - you know, even one tragedy prevented; even one suicide, or one child who accesses an unsecured weapon and has an accidental shooting; I think the program pays for itself, and it's well worth it.

Shortly after Newtown, the Daily Beast noted a 2004 report which called the idea of gun buybacks "badly flawed" — in part because of the expense to municipalities.

“Let’s say you pay $100 per gun, and you get 2,000 guns,” says Jon Vernick, co-director of the Johns Hopkins Center for Gun Policy and Research. “That’s $200,000—would it be money better spent elsewhere?”

This is the rationale used in Arizona. In 2010, the state passed a law mandating that weapons seized by police be turned over to licensed firearms dealers for sale. Cities argued that buyback programs were exempted from that rule, since they were donated, not seized. The bill signed yesterday closes that loophole. Reuters describes the debate.

Supporters of the measure said municipalities were wasting taxpayers' money by not realizing the revenue from reselling turned-in weapons.

Opponents argued that it sent the wrong message and that the state needed to focus on the broader issue of gun control.

Given that many of the weapons turned in are not functioning or of little value, it's not clear that reselling them would offset the cost of the gift cards. The most likely outcome of Arizona's new law, then, is that buyback programs will be curtailed. Why, as one legislator argued, "force the resale of guns that would otherwise never have been used for violence?"

The NRA, which apparently cringes at the site of a gun being melted or snapped in two, was enthusiastically supportive of the new rule. "[T]his measure would ensure that taxpayer resources are not utilized to pursue a political agenda of destroying firearms," an official with the organization wrote to the legislature.