Cal. Gov. Code § 8611

Counties, cities and counties, and cities may provide for the calling of test exercises, either singularly or jointly, whenever, in the opinion of such political subdivisions, such test exercises are needed; provided, however, that with respect to any such test exercise no one shall have the power to command the assistance of any private citizen, and the failure of a citizen to obey any order or regulation pertaining to a test exercise shall not constitute a violation of any law.