The federal Constitution provides that a judgment from a sister state (of the United States) is entitled to the same "full faith and credit" in every court within the United States as it has by law or usage in the court of the sister state. Thus, a sister state judgment rendered by a court with jurisdiction over the subject matter and the parties is given collateral estoppal (issue preclusion) and res judicata (claim preclusion) effect nationwide. However, procedurally, a sister state judgment is enforced in California pursuant to California law. A sister state judgment cannot be enforced in California until it is "domesticated" (or registered) in California as a California judgment in accordance with the Sister State Money-Judgments Act (the "SSMJA") or by bringing an action to establish the judgment per Code of Civil Procedure 1913.
Under the SSMJA (beginning at Code of Civil Procedure 1710.10), a money judgment obtained in another state may be filed with a California court and a California judgment is entered immediately. Once served on the judgment debtor, it becomes enforceable, and a writ of execution is generally issued.
After service of the judgment, the judgment debtor has 30 days to file and serve a motion to vacate the judgment. But the judgment may only be vacated upon certain specified and proven grounds: (1) the most common: the sister state court (that entered the judgment) lacked either subject matter or personal jurisdiction over the defendant; (2) there is an appeal of the judgment pending in the sister state; (3) the sister state court has granted a stay of enforcement, or (4) there is a motion to vacate the judgment pending in the sister state.