California Code, Welfare and Institutions Code - WIC § 17001.51

(a) A county may require adult applicants and recipients of benefits under the general assistance program to undergo screening for substance abuse when it is determined by the county that there is reasonable suspicion to believe that an individual is dependent upon illegal drugs or alcohol. The county shall maintain documentation of this finding.

(b) A county may require as a condition of aid reasonable participation in substance abuse or alcohol treatment programs for persons screened pursuant to subdivision (a) and professionally evaluated to be in need of treatment, if the services are actually available at no charge to the applicant or recipient.