FAM §7541: (a) If the court finds that the spouse who is a presumed parent under Section 7540 is not a genetic parent of the child pursuant to Chapter 2 (commencing with Section 7550), the question of parentage

(a) If the court finds that the spouse who is a presumed parent under Section 7540 is not a genetic parent of the child pursuant to Chapter 2 (commencing with Section 7550), the question of parentage shall be resolved in accordance with all other applicable provisions of this division, including, but not limited to, Section 7612. (b) An action to challenge the parentage of the spouse who is a presumed parent under Section 7540 shall be filed and served not later than two years from the child’s date of birth and may only be filed by any of the following: (1) By either spouse. (2) By a person who is a presumed parent under Section 7611 or by the child, through or by the child’s guardian ad litem, to establish the parentage of the person who is a presumed parent under Section 7611. (c) The petition or motion to challenge a presumption under Section 7540 pursuant to this section shall be supported by a declaration under oath submitted by the moving party stating the factual basis for placing the issue of parentage before the court. (d) Genetic testing may not be used to challenge parentage, in either of the following cases: (1) A case that reached final judgment of parentage on or before September 30, 1980. (2) A case challenging the parentage of a spouse who is a parent pursuant to Section 7962 or subdivision (a) of Section 7613, except to resolve a dispute regarding whether the child was conceived through assisted reproduction.