Cal. Gov. Code § 51058
From and after the time when an open-space easement has been accepted by the city or county and its acceptance endorsed thereon, no building permit may be issued for any structure which would violate the easement and the city or county shall seek by appropriate proceedings an injunction against any threatened construction or other development or activity on the land which would violate the easement and shall seek a mandatory injunction requiring the removal of any structure erected in violation of the easement.
In the event the county or city fails to seek an injunction against any threatened construction or other development or activity on the land which would violate the easement or to seek a mandatory injunction requiring the removal of any structure erected in violation of the easement, or if the county or city should construct any structure or development or conduct or permit any activity in violation of the easement, the owner of any property within the county or city, or any resident thereof, may, by appropriate proceedings, seek such an injunction.
Nothing in this chapter shall limit the power of the state, or any department or agency thereof, or any county, city, school district, or any other local public district, agency or entity, or any other person authorized by law, to acquire land subject to an open-space easement by eminent domain.
Ca. Gov. Code § 51058