Idaho Code § 40-903: County, city or highway district bid prohibited.

No county, city or highway district shall bid on any state highway system construction project which is let by competitive bid by the Idaho transportation board; provided, however, the provisions of this section shall not prohibit the Idaho transportation board, a county, a city or a highway district from entering into agreements with one another for joint or cooperative action pursuant to the provisions of chapter 3, title 40, or chapter 23, title 67, Idaho Code.