Cal. Fam. Code § 5700.611

(a) If Section 5700.613 does not apply, upon petition a tribunal of this state may modify a child-support order issued in another state which is registered in this state if, after notice and hearing, the tribunal finds that:
1. (1) the following requirements are met:
  1. (A) neither the child, nor the obligee who is an individual, nor the obligor resides in the issuing state;
  2. (B) a petitioner who is a nonresident of this state seeks modification; and
  3. (C) the respondent is subject to the personal jurisdiction of the tribunal of this state; or
2. (2) this state is the residence of the child, or a party who is an individual is subject to the personal jurisdiction of the tribunal of this state, and all of the parties who are individuals have filed consents in a record in the issuing tribunal for a tribunal of this state to modify the support order and assume continuing, exclusive jurisdiction.
(b) Modification of a registered child-support order is subject to the same requirements, procedures, and defenses that apply to the modification of an order issued by a tribunal of this state and the order may be enforced and satisfied in the same manner.
(c) A tribunal of this state may not modify any aspect of a child-support order that may not be modified under the law of the issuing state, including the duration of the obligation of support. If two or more tribunals have issued child-support orders for the same obligor and same child, the order that controls and must be so recognized under Section 5700.207 establishes the aspects of the support order which are nonmodifiable.
(d) In a proceeding to modify a child-support order, the law of the state that is determined to have issued the initial controlling order governs the duration of the obligation of support. The obligor’s fulfillment of the duty of support established by that order precludes imposition of a further obligation of support by a tribunal of this state.
(e) On the issuance of an order by a tribunal of this state modifying a child-support order issued in another state, the tribunal of this state becomes the tribunal having continuing, exclusive jurisdiction.
(f) Notwithstanding subsections (a) through (e) and Section 5700.201(b), a tribunal of this state retains jurisdiction to modify an order issued by a tribunal of this state if:
1. (1) one party resides in another state; and
2. (2) the other party resides outside the United States.