California Code, Streets and Highways Code - SHC § 100.21

(a) Whenever a street or highway closing agreement is required by Section 100.2, the department shall not acquire, except by gift, and except in hardship or protective cases as determined by the department or the commission, any real property for a freeway through a city until an agreement is first executed with the city council, or for a freeway through unincorporated territory in a county until an agreement is first executed with the board of supervisors. The department shall give notice to the city council or the board of supervisors, as the case may be, of any acquisition of real property prior to the execution of an agreement.

(b) Notwithstanding subdivision (a), a city council, or a county board of supervisors may, by resolution, authorize the purchase of rights-of-way prior to approval of an agreement if the purchase is limited to the mainline corridor of the proposed freeway and the alignment of the freeway is not at issue.