Cal. Civil Code § 3339.10

(a) The immigration or citizenship status of any person is irrelevant to any issue of liability or remedy under Chapter 2 (commencing with Section 1940) of Title 5 of Part 4 of Division 3, Chapter 2 (commencing with Section 789) of Title 2 of Part 2 of Division 2 of this code, or under Chapter 4 (commencing with Section 1159) of Title 3 of Part 3 of the Code of Civil Procedure, or in any civil action involving a tenant’s housing rights. (b) (1) In proceedings or discovery undertaken in a civil action to enforce Chapter 2 (commencing with Section 1940) of Title 5 of Part 4 of Division 3, Chapter 2 (commencing with Section 789) of Title 2 of Part 2 of Division 2 of this code, or under Chapter 4 (commencing with Section 1159) of Title 3 of Part 3 of the Code of Civil Procedure, or in any civil action involving a tenant’s housing rights, no inquiry shall be permitted into a person’s immigration or citizenship status, except as follows: (A) The tenant’s claims or defenses raised place the person’s immigration or citizenship status directly in contention. (B) The person seeking to make this inquiry demonstrates by clear and convincing evidence that this inquiry is necessary in order to comply with federal immigration law. (2) The assertion of an affirmative defense to an unlawful detainer action under Section 1161.4 of the Code of Civil Procedure does not constitute cause under this subdivision for discovery or other inquiry into that person’s immigration or citizenship status.