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 Missouri, 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 refrain from evaluating the legality of governmental actions taken by a foreign sovereign within its own territory. The rationale behind this doctrine is to respect the sovereignty of foreign nations and to avoid conflicts with executive branch policies in foreign relations. While Missouri state courts may apply the doctrine in cases that come before them, the act of state doctrine is primarily guided by U.S. Supreme Court precedents and federal case law. It is important to note that there are exceptions to the doctrine, such as when a U.S. statute or treaty explicitly indicates that certain foreign acts may be subject to judicial review in the United States.