Sam Girod is a Kentucky farmer who runs a small business selling natural skin salves made from herbs such as chickweed, which seem to help relieve a host of skin conditions, including allergic rashes, psoriasis, poison oak and even skin cancers. If you look up...

This would seem to embody the USDA’s advisory, “Know your farmer, know your food,” right? Not exactly. For the USDA and its sister food regulator, the FDA, there’s a problem: many of the farmers are distributing the food via private contracts like herd shares and...