Family Code Section 3427

(a) A court of this state that has jurisdiction under this part to make a child custody determination may decline to exercise its jurisdiction at any time if it determines that it is an inconvenient forum under the circumstances and that a court of another state is a more appropriate forum. The issue of inconvenient forum may be raised upon motion of a party, the court's own motion, or request of another court.

(b) Before determining whether it is an inconvenient forum, a court of this state shall consider whether it is appropriate for a court of another state to exercise jurisdiction. For this purpose, the court shall allow the parties to submit information and shall consider all relevant factors, including:

(1) Whether domestic violence has occurred and is likely to continue in the future and which state could best protect the parties and the child.

(2) The length of time the child has resided outside this state.

(3) The distance between the court in this state and the court in the state that would assume jurisdiction.

(4) The degree of financial hardship to the parties in litigating in one forum over the other.

(5) Any agreement of the parties as to which state should assume jurisdiction.

(6) The nature and location of the evidence required to resolve the pending litigation, including testimony of the child.

(7) The ability of the court of each state to decide the issue expeditiously and the procedures necessary to present the evidence.

(8) The familiarity of the court of each state with the facts and issues in the pending litigation.

(c) If a court of this state determines that it is an inconvenient forum and that a court of another state is a more appropriate forum, it shall stay the proceedings upon condition that a child custody proceeding be promptly commenced in another designated state and may impose any other condition the court considers just and proper.

(d) A court of this state may decline to exercise its jurisdiction under this part if a child custody determination is incidental to an action for dissolution of marriage or another proceeding while still retaining jurisdiction over the dissolution of marriage or other proceeding.

(e) If it appears to the court that it is clearly an inappropriate forum, the court may require the party who commenced the proceeding to pay, in addition to the costs of the proceeding in this state, necessary travel and other expenses, including attorney's fees, incurred by the other parties or their witnesses. Payment is to be made to the clerk of the court for remittance to the proper party.

(f)(1) In a case where the provision of gender-affirming health care or gender-affirming mental health care to the child is at issue, a court of this state shall not determine that it is an inconvenient forum where the law or policy of the other state that may take jurisdiction limits the ability of a parent to obtain gender-affirming health care or gender-affirming mental health care for their child.

(2) For the purposes of this section, “gender-affirming health care” and “gender-affirming mental health care” have the same meaning as defined by Section 16010.2 of the Welfare and Institutions Code.