Sec. 15. If a contractor uses a subcontractor to provide services for work the contractor is performing under a public contract for services or a contract for a public works project, the subcontractor shall certify to the contractor in a manner consistent with federal law that the subcontractor, at the time of certification:
(1) does not knowingly employ or contract with an unauthorized alien; and
(2) has enrolled and is participating in the E-Verify program.