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 Delaware, as in other U.S. states, the act of state doctrine is recognized and applied based on federal common law principles rather than state statutes. This doctrine holds that U.S. courts should not evaluate 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. While the act of state doctrine is a federal doctrine, its application can be relevant in state courts when they are dealing with cases that involve questions of international law or foreign sovereign acts. However, the doctrine is not absolute and can be subject to certain exceptions, such as when a specific treaty or statute provides otherwise, or when the foreign act in question violates international law or fundamental policies of the United States.