Cal. Civ. Code § 1940.45

(a) Except as otherwise provided by this section, a property owner shall not enforce or adopt a restrictive covenant or any other restriction that prohibits one or more religious items from being displayed or affixed on any entry door or entry door frame of a dwelling.
(b) To the extent permitted by Article 1, Section 4, of the California Constitution and the First Amendment to the United States Constitution, this section does not prohibit the enforcement or adoption of a restrictive covenant or
other restriction prohibiting the display or affixing of a religious item on any entry door or entry door frame to a dwelling that:
(1) Threatens the public health or safety.
(2) Hinders the opening or closing of any entry door.
(3) Violates any federal, state, or local law.
(4) Contains graphics, language or any display that is obscene or otherwise illegal.
(5) Individually or in combination with any other religious item displayed or affixed on any entry door or door frame that has a total size greater than 36 by 12
square inches, provided it does not exceed the size of the door.
(c) As used in this section, the following terms have the following meanings:
(1) “Property owner” means all of the following:
(A) An association, as that term is defined in Section 4080.
(B) A board, as that term is defined in Section 4085.
(C) A member, as that term is defined in Section
4160.
(D) A landlord, as that term is defined in Section 1940.8.5.
(E) A sublessor.
(2) “Religious item” means an item displayed because of sincerely held religious beliefs.