Act of state doctrine

The act-of-state doctrine is a principle in international law whereby acts done by a state in its own territory cannot be challenged by the national courts of another state.

As a principle of federal common law in the United States which states, in circumstances where it applies, that courts in the United States will not rule on the validity of another government's (formal) sovereign act with respect to property located within the latter's own territory. The act-of-state doctrine enters consideration most often in cases where a foreign sovereign has expropriated the property of a U.S. national located in that foreign territory (e.g. through nationalization).