California Code, Public Resources Code - PRC § 5157

Any county may purchase or lease, or obtain by gift, lands located in the county, or in other counties and may hold, improve, and maintain such lands for public parks, public beaches, public recreation areas or public boulevards.

Before land situated in another county may be so acquired and held, improved, and maintained, the consent by resolution of the board of supervisors of that county shall be obtained.  Land acquired in conformity with the requirements of this section is subject to the jurisdiction, laws and ordinances of the acquiring county.