California Code, Public Resources Code - PRC § 5401

(a) No city, city and county, county, public district, or agency of the state, including any division, department or agency of the state government, or public utility, shall acquire (by purchase, exchange, condemnation, or otherwise) any real property, which property is in use as a public park at the time of such acquisition, for the purpose of utilizing such property for any nonpark purpose, unless the acquiring entity pays or transfers to the legislative body of the entity operating the park sufficient compensation or land, or both, as required by the provisions of this chapter to enable the operating entity to replace the park land and the facilities thereon.

(b) Where the operating entity and the acquiring entity are one and the same, the entity is subject to the provisions of this chapter pertaining to both operating and acquiring entities, and the entity is, as acquiring entity, required to make funds or land, or both, available pursuant to Section 5405 or 5407.2, and, as operating entity, required to acquire or improve park lands and facilities pursuant to Sections 5404, 5407, 5407.1, and 5407.2.