“Respect for workers worldwide.”
The Ethical Trading Initiative accepts companies that, at a minimum, satisfy the labor standards set forth in their Base Code. Although they don’t actively police, they can assure ethics-minded consumers that the companies who take part in the ETI aren’t enslaving workers, gravely mistreating them, or employing children. They also provide news about international labor issues and firsthand accounts of factory life.
The base code is not as strict as I would like, but it’s a place to start if you’re wary of leaving the fast fashion market altogether. You can see a list of approved companies here.