Legal Question in Employment Law in California

Nice try, but the law does not protect illegal activity, like drug use. Failing a drug test or being discovered at work under the influence is grounds for immediate termination for cause / misconduct, with denial of unemployment benefits and COBRA insurance coverage. The courts have consistently supported the 'drug free workplace' policies.

Had you approached your employer voluntarily seeking help, many will cooperate with employees they like, to arrange counseling and rehab, and hold your job. That is voluntary, not mandatory.