Michael Hobbes has an eye-opening story in Highline, The Huffington Post’s features and investigations vertical, about why it’s impossible to eliminate sweatshops through boycotting and shopping ethically alone. Here’s how Wal-Mart found itself producing clothes at an unsafe garment factory despite banning its suppliers from using it:

After the Tazreen fire, NGO campaigns focused on how Wal-Mart was responsible for 60 percent of the clothing being produced there. But Wal-Mart never actually placed an order with Tazreen. In fact, over a year before the fire, Wal-Mart inspected the factory and discovered that it was unsafe. By the time of the fire, it had banned its suppliers from using it.

So here’s how its products ended up at Tazreen anyway: Wal-Mart hired a megasupplier called Success Apparel to fill an order for shorts. Success hired another company, Simco, to carry out the work. Simco—without telling Success, much less Wal-Mart—sub-contracted 7…