This chapter begins with a review of the historical origins of the Alien Tort Statute (ATS). It traces the modern application of the statute from the landmark decision in Filartiga v. Pena-Irala through the Supreme Court's endorsement of human rights litigation in Sosa v. Alvarez-Machain. The Karadzic court's recognition that private actors are both bound by some international law norms and can be held liable when they act in concert with state actors paved the way for ATS litigation against corporations. The Supreme Court granted petitions for certiorari review on both issues: the false arrest claim against the U.S. government and the ATS claim against Sosa. The chapter concludes with a review of post-Sosa application of the ATS and the issues left open by the Supreme Court's decision.  Keywords: Alien Tort Statute (ATS), Alvarez-Machain, Filartiga, Sosa