The act of state doctrine is a court-made (common law) doctrine that prohibits U.S. courts from judging the validity of the official acts of a foreign country that take place within that foreign country's borders.
In California, as in other U.S. states, the act of state doctrine is recognized and applied based on federal common law, rather than state statutes. This doctrine holds that U.S. courts will generally not examine or question the validity of public acts performed by a recognized foreign sovereign within its own territory. The rationale behind this doctrine is to respect the sovereignty of foreign nations and to avoid conflicts in foreign relations that could arise from the judicial review of such acts. However, the doctrine is not absolute and may not apply in certain circumstances, such as when a clear violation of international law is present or when the U.S. has a strong policy interest in adjudicating the matter. The U.S. Supreme Court has the ultimate authority in interpreting the scope and exceptions to the act of state doctrine, and its decisions are binding on California courts.