What’s not to like about reusable shopping bags? “People put things in them, and then at the register, they’ll pull out a third of the stuff to pay for. That’s one trick,” says Bob Sparrow, owner of Kerrytown’s Sparrow Market. Another is to load up a reusable shopping bag and sidle out the door, bypassing the cash register completely.

In the last year, “we’ve caught four people who I’ve known for twenty or twenty-five years,” Sparrow says. “With each of them, I’ve watched them steal groceries three or four times before I confronted them.”

Sparrow says he can’t afford to prosecute. “I can’t spend five or six hours in court for twenty dollars’ worth of groceries,” he sighs. “The police say that the ‘social norm’ is to put groceries in a ‘business-provided basket,'” and Sparrow would be within his rights to post a sign requiring people to use them. But, aware that Kerrytown’s small-town friendliness is part of its appeal, he’s reluctant to go that far. “If we start policing our customers, they’ll just go to Whole Foods, where there’s free parking.”

Sparrow says that reusable bags can also lead to accidental shoplifting. Customers will “have a wad of other bags in there, along with their phone, their wallet,” he explains. “So something like this”–he holds up a long, skinny bratwurst he’s wrapping up for a customer–“can easily get lost on the bottom. And when they get home, they’re embarrassed to call back and tell me.”