California Code, Vehicle Code - VEH § 12806

(a) Who is rendered incapable of safely operating a motor vehicle because of alcoholism, excessive and chronic use of alcoholic beverages, or addiction to, or habitual use of, any drug.

(b) Who is addicted to the use of narcotic drugs unless the person is participating in a narcotic treatment program approved pursuant to Article 3 (commencing with Section 11875) of Chapter 1 of Part 3 of Division 10.5 of the Health and Safety Code, in which case the person may be issued a probationary license, subject to reasonable terms and conditions, if that drug usage does not affect the person's ability to exercise reasonable and ordinary control in operating a motor vehicle on the highway.

(c) Who has a disorder characterized by lapses of consciousness or who has experienced, within the last three years, either a lapse of consciousness or an episode of marked confusion caused by any condition which may bring about recurrent lapses, or who has any physical or mental disability, disease, or disorder which could affect the safe operation of a motor vehicle unless the department has medical information which indicates the person may safely operate a motor vehicle. In making its determination, the department may rely on any relevant information available to the department.