Cal. Fam. Code § 3447

If a proceeding for enforcement under this chapter is commenced in a court of this state and the court determines that a proceeding to modify the determination is pending in a court of another state having jurisdiction to modify the determination under Chapter 2 (commencing with Section 3421), the enforcing court shall immediately communicate with the modifying court. The proceeding for enforcement continues unless the enforcing court, after consultation with the modifying court, stays or dismisses the proceeding.