16 CFR §260.9 Free-of Claims
(a) It is deceptive to misrepresent, directly or by implication, that a product, package, or service is free of, or does not contain or use, a substance. Such claims should be clearly and prominently qualified to the extent necessary to avoid deception.
(b) A truthful claim that a product, package, or service is free of, or does not contain or use, a substance may nevertheless be deceptive if: (1) the product, package, or service contains or uses substances that pose the same or similar environmental risks as the substance that is not present; or (2) the substance has not been associated with the product category.
(c) Depending on the context, a free-of or does-not-contain claim is appropriate even for a product, package, or service that contains or uses a trace amount of a substance if: (1) the level of the specified substance is no more than that which would be found as an acknowledged trace contaminant or background level;4 (2) the substance’s presence does not cause material harm that consumers typically associate with that substance; and (3) the substance has not been added intentionally to the product.