Idaho Code § 40-1406

The highway commissioners of a county-wide highway district shall exercise all of the powers and duties provided in chapter 13 of this title, and are empowered to make highway ad valorem tax levies as provided by chapter 8, of this title. Only one (1) county-wide highway district shall be operative within a county where the electorate has voted affirmatively for the formation of a county-wide highway district. The district shall specifically be responsible for all county secondary and city highways and is hereby recognized as a body politic of this state. No city included within a county-wide highway district shall maintain or supervise any city highways, or levy any ad valorem taxes for the construction, repair or maintenance of city highways. No highway district included within a county-wide highway district, shall maintain any secondary highways or levy any ad valorem taxes for the construction, repair or maintenance of highways. Wherever any provisions of the existing laws of the state of Idaho are in conflict with the provisions of this chapter, the provisions of this chapter shall control and supersede all such laws. However, within the limits of any city, the city may expend city funds for the placement, care and removal of trees, shrubs, grass, and other plants, which are located within the rights-of-way of any highway of the county-wide highway district.