As its term indicates, multinational corporations (MNCs) operate in many states and the question addressed in this chapter is what international law can tell us about the regulation of the activities of these entities. Is this solely the responsibility of the “host” state, or are other countries, most notably the “home” state, required to regulate harmful practices as well? The Alien Tort Statute (ATS) had been an important tool used against corporate transgressions under which foreign nationals were able to bring suit in federal court in the United States on the basis that a MNC had acted in violation of international law. However, the U.S. Supreme Court has recently narrowed the scope of the ATS so that the plaintiffs now have to establish a substantial connection to the United States.