FAM §3445: (a) A child custody determination issued by a court of another state may be registered in this state, with or without a simultaneous request for enforcement, by sending all of the following to the app

(a) A child custody determination issued by a court of another state may be registered in this state, with or without a simultaneous request for enforcement, by sending all of the following to the appropriate court in this state: (1) A letter or other document requesting registration. (2) Two copies, including one certified copy, of the determination sought to be registered, and a statement under penalty of perjury that to the best of the knowledge and belief of the person seeking registration the order has not been modified. (3) Except as otherwise provided in Section 3429, the name and address of the person seeking registration and any parent or person acting as a parent who has been awarded custody or visitation in the child custody determination sought to be registered. (b) On receipt of the documents required by subdivision (a), the registering court shall do both of the following: (1) Cause the determination to be filed as a foreign judgment, together with one copy of any accompanying documents and information, regardless of their form. (2) Serve notice upon the persons named pursuant to paragraph (3) of subdivision (a) and provide them with an opportunity to contest the registration in accordance with this section. (c) The notice required by paragraph (2) of subdivision (b) shall state all of the following: (1) That a registered determination is enforceable as of the date of the registration in the same manner as a determination issued by a court of this state. (2) That a hearing to contest the validity of the registered determination must be requested within 20 days after service of the notice. (3) That failure to contest the registration will result in confirmation of the child custody determination and preclude further contest of that determination with respect to any matter that could have been asserted. (d) A person seeking to contest the validity of a registered order must request a hearing within 20 days after service of the notice. At that hearing, the court shall confirm the registered order unless the person contesting registration establishes any of the following: (1) That the issuing court did not have jurisdiction under Chapter 2 (commencing with Section 3421). (2) That the child custody determination sought to be registered has been vacated, stayed, or modified by a court having jurisdiction to do so under Chapter 2 (commencing with Section 3421). (3) That the person contesting registration was entitled to notice, but notice was not given in accordance with the standards of Section 3408, in the proceedings before the court that issued the order for which registration is sought. (e) If a timely request for a hearing to contest the validity of the registration is not made, the registration is confirmed as a matter of law and the person requesting registration and all persons served shall be notified of the confirmation. (f) Confirmation of a registered order, whether by operation of law or after notice and hearing, precludes further contest of the order with respect to any matter that could have been asserted at the time of registration.