With respect to the ATS, however, the debate among the concurring justices focused on how limited the reach of the ATS would be in other potential cases where the connection to the United States was more substantial than the facts presented in Kiobel.   Along this spectrum of potential cases, the justices agreed generally that under the Supreme Court’s prior ATS decision in Sosa v. Alvarez-Machain, 542 U.S. 692 (2004), the ATS could reach cases involving foreign ambassadors in the United States because these incidents were historically a source of international friction at the time the ATS was drafted.   Invoking Sosa, the justices also agreed that claims based on piracy would be cognizable under the ATS although occurring outside of the United States’ territorial jurisdiction. 

From there, however, there was little apparent agreement as to what other violations of international could give rise to an ATS claim, or what contacts with the United States would be necessary to sustain such a claim.   For example, the Court’s opinion, written by Chief Justice Roberts, took a very narrow and historical view of the ATS substantively, which limited the interpretation of the jurisdictional reach of the federal courts to entertain claims for violations of the law of nations that occur on foreign soil.   Justice Breyer, on the other hand, would not have invoked the American presumption against extraterritoriality in applying the ATS at all.  Rather, because the jurisdictional question is inherently tied to the law of nations to be enforced through the ATS, Justice Breyer argued that the jurisdictional question should also be guided in part by “principles and practices of foreign relations law,” which would allow for a court to exercise jurisdiction (given the potential foreign relations pitfalls of entertaining such cases) only where “(1) the alleged tort occurs on American soil, (2) the defendant is an Amer­ican national, or (3) the defendant’s conduct substantially and adversely affects an important American national interest, and that includes a distinct interest in prevent­ing the United States from becoming a safe harbor (free of civil as well as criminal liability) for a torturer or other common enemy of mankind.”

Although Justice Breyer relied on international law in developing his ATS formulation, he acknowledged that principles of judicial and constitutional restraint impose broader restrictions on the court’s adjudicatory authority to hear cases under the ATS.  Indeed, under international law, states may exercise prescriptive jurisdiction based on several factual situations beyond those recognized in Justice Breyer’s concurring opinion.  For example, as indicated in Section 402 of the Restatement (Third) of the Foreign Relations Law of the United States, a nation’s prescriptive authority can reach conduct occurring within its territory (the principle of territoriality), foreign conduct having a substantial effect in its territory (the effects principle), foreign conduct committed by domestic nationals (the nationality principle), foreign conduct that threatens domestic security (the protective principle), and foreign conduct injuring domestic nationals abroad (passive personality principle).   All such exercises of prescriptive jurisdiction are subject to the limitations of reasonableness, as indicated in Section 403 of the Restatement.

With Kiobel’s limited holding focused only on the presumption of extraterritoriality in cases involving only tangential contacts with the United States, the future of ATS claims based on violations of international human rights law remains uncertain.  The role of international law in interpreting the ATS also remains in doubt, not only when it comes to determining the substantive and jurisdictional scope of the statute. By skirting the issue of whether corporations could be held liable under the ATS for violations of the law of nations, the incentive for potential plaintiffs to pursue corporate defendants to seek redress has not been negated. But as Kiobel demonstrates, when this issue does finally become the focus of the Supreme Court’s decision-making authority, the impact and role of international law in deciding that issue may be limited at best.