Every contractor on a public works project or improvement or hazardous waste clean-up and on-site disposal project in this State may place on such work no more than 3, or 6 in the case of a hazardous waste clean-up and on-site disposal project, of his regularly employed non-resident executive and technical experts, even though they do not qualify as Illinois laborers as defined in Section 1 of this Act.
30 ILCS 570/4