29 CFR § 570.116 - Separate applicability.
There are situations where section 12(c) does not apply because the minor himself is not considered employed in commerce or in the production of goods for commerce. This does not exclude the possibility of coverage under the provisions of section 12(a), however. In those cases where oppressive child labor is employed in commerce but not in or about a producing establishment, coverage exists under section 12(c) but not under the provisions of section 12(a). The employment of telegraph messengers under 16 years of age would normally involve this type of situation. 27 There may also be cases where oppressive child labor is employed in occupations closely related and directly essential to the production of goods in a separate establishment and therefore covered by section 12(c) but due to the fact that none of the goods produced in the establishment where the minors work are ever shipped or delivered for shipment in commerce either in the same form or as a part or ingredient of other goods, coverage of section 12(a) is lacking. An illustration of this type of situation would be the employment of a minor under the applicable age minimum in a plant engaged in the production of electricity which is sold and consumed exclusively within the same State and some of which is used by establishments in the production of goods for commerce.
27 In “Western Union Telegraph Co. v. Lenroot,” 323 U.S. 490, the court held section 12(a) inapplicable to Western Union on the grounds that the company does not “produce” or “ship” goods within the meaning of that subsection.