The U.S. Department of Agriculture's Food Service and Inspection Service compels producers of so-called free-range poultry to demonstrate that the birds in question have "been allowed access to the outside." Natural poultry contains no artificial ingredients or added color and is only minimally processed.

And that's it for USDA regulations.

Now, the department also publishes a document called "U.S. Trade Descriptions for Poultry" that outlines voluntary trade standards for chicken and chicken products. The trade descriptions specify six categories of poultry, each one comprising a production method (where the birds live) and a feeding system (what the birds eat).

Source: Baltimoresun.com