29 U.S.C. § 215 : US Code - Section 215: Prohibited acts; prima facie evidence

      (a) After the expiration of one hundred and twenty days from June
    25, 1938, it shall be unlawful for any person - 
        (1) to transport, offer for transportation, ship, deliver, or
      sell in commerce, or to ship, deliver, or sell with knowledge
      that shipment or delivery or sale thereof in commerce is
      intended, any goods in the production of which any employee was
      employed in violation of section 206 or section 207 of this
      title, or in violation of any regulation or order of the
      Secretary issued under section 214 of this title; except that no
      provision of this chapter shall impose any liability upon any
      common carrier for the transportation in commerce in the regular
      course of its business of any goods not produced by such common
      carrier, and no provision of this chapter shall excuse any common
      carrier from its obligation to accept any goods for
      transportation; and except that any such transportation, offer,
      shipment, delivery, or sale of such goods by a purchaser who
      acquired them in good faith in reliance on written assurance from
      the producer that the goods were produced in compliance with the
      requirements of this chapter, and who acquired such goods for
      value without notice of any such violation, shall not be deemed
      unlawful;
        (2) to violate any of the provisions of section 206 or section
      207 of this title, or any of the provisions of any regulation or
      order of the Secretary issued under section 214 of this title;
        (3) to discharge or in any other manner discriminate against
      any employee because such employee has filed any complaint or
      instituted or caused to be instituted any proceeding under or
      related to this chapter, or has testified or is about to testify
      in any such proceeding, or has served or is about to serve on an
      industry committee;
        (4) to violate any of the provisions of section 212 of this
      title;
        (5) to violate any of the provisions of section 211(c) of this
      title, or any regulation or order made or continued in effect
      under the provisions of section 211(d) of this title, or to make
      any statement, report, or record filed or kept pursuant to the
      provisions of such section or of any regulation or order
      thereunder, knowing such statement, report, or record to be false
      in a material respect.

      (b) For the purposes of subsection (a)(1) of this section proof
    that any employee was employed in any place of employment where
    goods shipped or sold in commerce were produced, within ninety days
    prior to the removal of the goods from such place of employment,
    shall be prima facie evidence that such employee was engaged in the
    production of such goods.