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 Montana, as in other U.S. states, the act of state doctrine is recognized as a principle of federal common law rather than state statute. This doctrine suggests that Montana courts, like all U.S. courts, are generally prohibited from evaluating the legality of official acts conducted 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 foreign policy. However, the application of the act of state doctrine is subject to certain exceptions and may be overridden by federal law or international agreements. It is important to note that while the doctrine is applied in federal and state courts, its contours and exceptions are primarily shaped by U.S. Supreme Court precedents and federal policy considerations.