A federal rule most "free-of" marketing claims quietly ignore.
The FTC's Guides for the Use of Environmental Marketing Claims (16 CFR Part 260) — commonly called the Green Guides — govern how environmental claims can be advertised in the United States. Section 260.9 addresses "free-of" claims directly, and its core principle is stated plainly: a reasonable consumer interprets a "free-of" claim to mean the product's manufacture doesn't cause any of the environmental or health risk associated with that substance [1].
The rule does allow trace amounts to be present without making the claim deceptive — but only under specific, evidenced conditions: the substance must be present in trace amounts in the environment generally, the product must emit less than what's typically present in that general environment, and the trace level present must not cause the material harm consumers associate with the substance.
A bare "microplastic-free" claim, with no stated method, no stated matrix, and no substantiation file on record, does not meet this bar. That's the direct reason the MPFREE claims policy requires every public claim to name the method, the matrix, and the Standard version it was tested under — the scoped-claim pattern is the substantiation the Green Guides actually require, not an optional stylistic choice.