What makes an ESA letter valid in California?

What the law says

Cal. Health & Safety Code § 122319(a) requires that the practitioner "is licensed or certified to provide professional services within the scope of the license or certification in this state" (§ 122319(a)(1)) and "has established a client-provider relationship with the individual at least 30 days prior to providing the documentation" (§ 122319(a)(2)).

Source: Cal. Health & Safety Code § 122319 ↗

In plain language

In California, an ESA letter is treated as valid documentation only when it comes from a clinician who holds an active California license and who has had an established client-provider relationship with the individual for at least 30 days before signing. That is a higher bar than the federal HUD standard, which does not fix a relationship length. A letter that satisfies the federal standard but not California's in-state-license and 30-day requirements may fall short under California law. Whether a particular clinician relationship meets these requirements is fact-specific and is a question for a California-licensed attorney.