Cal. Sts. & High. Code § 1624

The board of supervisors of any county may, as provided in Section 1625, expend any portion of the amounts paid to that county, and deposited in the road fund, for the acquisition of rights-of-way and the construction of any public highway outside of its county limits, whenever such construction is authorized by ordinance or resolution of the board of supervisors of the county in which the highway is to be constructed or for the acquisition of rights-of-way for, or the construction, improvement or maintenance of, any State highway pursuant to a contract made as provided in Section 130.