Different countries implement international law in a variety of ways.  The domestic recognition of customary international law, otherwise known as the law of nations, is even more vexing without the express language of a treaty to guide interpretation and execution.   In the United States, judicial enforcement of norms of customary international law in the absence of an express congressional statute has caused considerable debate among American judges and scholars.  The debate is even more pointed in the field of international human rights law, primarily because a significant amount of jurisprudential and historical ambiguity exists about whether the federal courts have jurisdiction to hear these claims under the Alien Tort Statute (ATS).

As originally enacted in 1789, the ATS provided that the federal courts would have jurisdiction, “concurrent with the courts of the several States, or the circuit courts, as the case may be, of all causes where an alien sues for a tort only in violation of the law of nations or a treaty of the United States.” In its current form, codified at 28 U.S.C. § 1350, the ATS states simply that jurisdiction exists in the federal courts for “any civil action by an alien for a tort only, committed in violation of the law of nations or a treaty of the United States.”

The first Supreme Court decision interpreting the scope of the ATS was not handed down until 2004 in Sosa v. Alvarez-Machain, 542 U.S. 692, 124 S. Ct. 2739 (2004).  In Sosa, the Supreme Court held in a 9-0 decision that the ATS did not provide jurisdiction for a claim raised by a Mexican national that he was abducted illegally from Mexico and brought to the United States to stand trial for the murder of a federal drug enforcement agent.  The plaintiff alleged that the federal Drug Enforcement Agency (DEA) had approved the plan, and asserted claims under both the Federal Tort Claims Act and for tort relief for violation of the law of nations, basing jurisdiction on the ATS.

In holding that Alvarez-Machain’s claim was not cognizable under the ATS, the Supreme Court did an extensive review of the history of the statute and determined as a preliminary matter that the statute itself is purely jurisdictional and does not create any cause of action.  The substance of the claim would have to be established by showing a “tort” in violation of the law of nations or a treaty.  Looking narrowly as to what claims would qualify for such a cause of action, the Supreme Court traced the history of various claims that were recognized at common law as being part of the law of nations, such as piracy, harm to ambassadors and diplomats, and certain mercantile rights.  As the Supreme Court stated, “[i]t was this narrow set of violations of the law of nations, admitting of a judicial remedy and at the same time threatening serious consequences in international affairs, that was probably on minds of the men who drafted the ATS with its reference to tort.” 

Even so, the Court (in an opinion by Justice Souter) acknowledged that the lower courts may further refine and develop the sorts of current customary international law norms of the same type and magnitude as recognized by the framers of the ATS.  Although Justice Scalia, joined by then-Chief Justice Rehnquist and Justice Thomas, agreed with the result that the ATS claim should be dismissed, he expressed objection to the “reservation of a discretionary power in the Federal Judiciary to create causes of action for the enforcement of international-law-based norms.”  According to Justice Scalia in his concurring opinion in Sosa, “[t]he notion that a law of nations, redefined to mean the consensus of states on any subject, can be used by a private citizen to control a sovereign's treatment of its own citizens within its own territory is a 20th-century invention of internationalist law professors and human rights advocates.”

Since Sosa was decided in 2004, lower federal courts have continued to recognize international human rights violations as actionable under the ATS.  Before Sosa, the leading federal case on the ATS was Filartiga v. Pena-Irala, 630 F.2d 876 (2d Cir. 1980), which paved the way for claims brought by aliens for violation of certain customary international law norms involving human rights.  After Sosa, which did not expressly close the door to such claims, a number of high profile human rights cases have been filed in the lower federal courts under the jurisdictional grant of the ATS.  For example, in Vietnam Ass’n for Victims of Agent Orange v. Dow Chemical Co., 517 F.3d 104 (2d Cir. 2008), the court held that the manufacture and supply of an herbicide used as a defoliant did not violate international law, and thus was not actionable under the ATS, so long as it was not used intentionally to harm humans.  In Mora v. New York, 524 F.3d 183 (2d Cir. 2008), the Second Circuit further held that detention without notice of consular rights did not violate well-accepted norms of customary international law.  Finally, in Abdullahi v. Pfizer, Inc., 562 F.3d 163 (2d Cir. 2009), a divided panel held “that the prohibition in customary international law against nonconsensual human medical experimentation can[ ] be enforced through the ATS.” Id. at 169.

An important emerging issue in ATS claims is the extent of accessorial liability for corporations that do business with governments accused of committing mass violations of human rights.  Recently, this precise issue was addressed by the Second Circuit in Presbyterian Church of Sudan v. Talisman Energy, Inc., 582 F.3d 244 (2d Cir. 2009), which involved ATS claims brought by Sudanese nationals who alleged that they were victims of human rights abuses committed by the Government of the Sudan.  The Talisman case was brought against a Canadian corporation on the grounds that it aided and abetted the Sudanese government in its human rights violations in order to secure oil concessions.  The district court granted summary judgment in favor of the Canadian corporation, and the Second Circuit affirmed, finding that plaintiffs needed to provide proof that the corporation provided substantial assistance to the Sudanese Government in committing crimes against humanity with the purpose of aiding the government's unlawful conduct.  Looking to international law to find the standard for accessorial liability, the Second Circuit held that the mens rea standard for aiding and abetting liability in ATS actions is purpose rather than knowledge of the violations alone.   In reaching this conclusion, the Second Circuit determined that there was “sufficient international consensus for imposing liability on individuals who purposefully aid and abet a violation of international law.”