290.560. Whenever there is a period of excessiveunemployment in this state, every person who is charged with theduty, either by law or contract, of constructing or building anypublic works project or improvement for the state or anypolitical subdivision, municipal corporation or othergovernmental unit thereof shall employ only Missouri laborers andlaborers from nonrestrictive states on such project orimprovement, and every contract let by any such person shallcontain a provision requiring that such labor be used, exceptthat other laborers may be used when Missouri laborers orlaborers from nonrestrictive states are not available, or areincapable of performing the particular type of work involved, ifso certified by the contractor and approved by the contractingofficer.
(L. 1993 H.B. 416 & 417 ยง 3)