THE offices of the Dix Scrap Iron & Metal Company, a scrapyard in south-west Detroit, resemble an outlaw’s holdout. A rifle is propped up behind the desk of the owner, John Dingell III (incidentally, the son of a former congressman). Holes are patched in the wood-panelled walls where thieves have broken in to raid the safe or to steal metal from the warehouse behind. Several more guns are concealed about the smoky room, which Mr Dingell shares with a colleague who helps provide security. The business has been in Detroit since 1935. Yet it is now closing down. Its end may signal the decline of one of Detroit’s few thriving industries: the sale of scrap salvaged or stolen from the city’s many empty houses and businesses.

Motown has always had scrap-metal dealers—the car industry bends a lot of metal. The business grew frenetic after the economic crisis hit: tens of thousands of homes and factories were made derelict by foreclosure just as global metal prices soared. Many jobless Detroiters made a living by raiding empty buildings for copper wiring or stainless steel fittings.

This has not been good for the city. At Southwestern High School, a mile or so from Mr Dingell’s scrapyard, little is left of the grand building, which closed to pupils in 2012. Thieves have taken every locker door, torn out every strand of cabling and fully dismantled what was once a covered walkway. In the tiled swimming pool, broken furniture is frozen in place in about two feet of murky ice. The city authorities hoped to sell the building to developers. Instead, it seems likely to join thousands of other looted buildings, most of which would cost more to repair than the land they sit on is worth.

Scrapping is now slowing, for several reasons. First, the easiest pickings have gone. Few empty houses still have copper wiring to steal, and the most dedicated thieves have taken to robbing working businesses, rather than empty ones. Second, metal prices have fallen dramatically over the past year: the price of copper has fallen by nearly a quarter. For businesses such as Mr Dingell’s, however, the biggest problem is a new law passed in Michigan last year to stop the metal-strippers.

In the past, scrap-dealers mostly dealt with customers fairly informally. They had to record the identity and fingerprints of most of the people bringing them scrap, but they could still pay in cash instantly. Under the new law, scrappers are required to make any payment of $25 or more by post, sending either a cheque or a bank card which can be used only at an on-site machine fitted with a camera. This, hopes Rashida Tlaib, the Detroit politician behind the measure, will deter criminals, or else make it easier to prosecute them. “I was seeing my neighbourhood being destroyed by these almost invisible transactions,” she says.

Mr Dingell says that the new law is driving him out of business and having “precisely zero” effect on thieves. They already mostly sell their wares to fences who will find ways round the new rules, he thinks; most metal can be melted down or cut up so that its origin is unidentifiable. Posting cheques would expose him to identity theft, while installing an ATM would give the thieves yet another thing to steal. Theft should be tackled at its root, he says: when Southwestern High School was first looted, he tipped off the local sergeant, who did nothing.

But with limited resources, it is difficult to respond to every crime. In 2013, 316 people were murdered in Detroit, almost as many as in New York City, which is 12 times larger. Its police officers are poorly paid and overworked. And with every house torn up, the city becomes a little harder to save. Perhaps the fewer scrappers there are, the better its chances.