The power of Congress to define “offenses against the law of nations” encompasses three subjects: 1) piracies and 2) felonies committed on the high seas, and 3) offenses against the law of nations. At the time of the framing, piracy was the only universal crime contrary to the law of nations, and Congress quickly dealt with it in a 1790 statute. (See Piracy and Felonies Clause) But although piracy is defined by the law of nations, “felonies committed on the high seas,” such as murder, must be specifically defined by Congress. United States v. Furlong (1820). Determining the grounds on which Congress can define offenses against the law of nations, however, has been more difficult.

The inability of the government to conduct foreign affairs effectively under the Articles of Confederation led the Continental Congress to pass a resolution in 1781 asking the states to “provide expeditious, exemplary and adequate punishment . . . for the infractions of the immunities of ambassadors and other public ministers, authorized and received as such by the United States in Congress assembled.” Leaving the issue in the hands of the states, however, impelled Edmund Randolph, in his opening speech to the Constitutional Convention in 1787, to emphasize that this was one of the major defects of the Articles of Confederation.

At the Constitutional Convention, the Article I, Section 8, Clause 10 went through a number of redactions. At one point, Gouverneur Morris thought the term “define” too rigid (as applied to piracy and felonies), because it was “limited to preexisting meaning.” He thought “designate” might give Congress more discretion. But other delegates insisted that “define” was broad enough to be “applicable to the creating of offenses also,” as the Supreme Court would later affirm in Furlong.

Gouverneur Morris then later argued that Congress should also have the power to “define” offenses against the law of nations, but James Wilson expressed a concern. “To pretend to define the law of nations which depended on the authority of all the Civilized Nations of the World, would have the look of arrogance, that would make us look ridiculous.” But Gouverneur Morris thought that Congress must be given the discretion to make specific what may be ambiguous. He responded: “The word define is proper when applied to offenses in this case; the law of nations being often too vague and deficient to be a rule.” This time, Morris’s position prevailed and was later supported by Justice Joseph Story in the seminal case of United States v. Smith (1820): “Offences, too, against the law of nations, cannot, with any accuracy, be said to be completely ascertained and defined in any public code recognized by the common consent of nations.” Story continued, “[T]here is a peculiar fitness in giving the power to define as well as to punish; and there is not the slightest reason to doubt that this consideration had very great weight in producing the phraseology in question.”

The question of the range of discretion possessed by Congress in defining what is an offense against the law of nations has continued to be debated. In the main, the judiciary has regarded Congress’s power as limited by what is objectively part of the law of nations, but has accorded discretion to Congress in making such a determination. In United States v. Arjona (1887), the Court declared that Congress need not formally define an offense as “against the law of nations” in a statute that criminalized counterfeiting foreign securities, so long as it was punishing an action that was in fact contrary to customary international law. The Court stated, “[I]f the thing made punishable is one which the United States are required by their international obligations to use due diligence to prevent, it is an offense against the law of nations.” However, the Court insisted, “Whether the offense as defined is an offense against the law of nations depends on the thing done, not on any declaration to that effect by congress.”

Similarly, in Ex parte Quirin (1942), the Court upheld Congress’s statutory establishment of military commissions to try enemy aliens when it “incorporated by reference . . . all offenses which are defined as such by the law of war,” itself a part of the law of nations.

In Sosa v. Alvarez-Machain (2004), the Court was forced to confront its own power in defining offenses against the law of nations. The case dealt with the meaning of the Alien Tort Statute, which Congress had enacted as part of the Judiciary Act of 1789. The statute read, “The district courts shall have original jurisdiction of 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 Court concluded that the Alien Tort Statute did not grant the courts any new causes of action, but only allowed for jurisdiction to hear individual suits based on common law violations of the law of nations that existed at the time of the founding, such as infringement of safe conducts, diplomatic immunity, or piracy. Because the Supreme Court later rejected the idea of a “federal common law” (Erie v. Tompkins (1938)), the Alien Tort Statute has only limited scope: there remains but a “narrow class of international norms” that the Court could recognize and enforce. In concurrence in Sosa, Justice Antonin Scalia insisted that the courts could enforce such rules, but not on its own cognizance of them. Rather, the courts have jurisdiction over such offenses only because Congress has authorized them to do so.

In recent years, the courts have begun a more detailed examination of the meaning and the limits of the clause. The Offenses against the Law of Nations provision made a brief, but consequential, appearance in the Supreme Court’s decision of Hamdan v. Rumsfeld (2006). Hamdan had been charged with conspiracy to commit acts of terrorism. The Court noted that Congress had not specifically defined “conspiracy” as an offense against the law of nations. Rather, through Article 21 of the Uniform Code of Military Justice, Congress has “‘incorporated by reference’ the common law of war, which may render triable by military commission certain offenses not defined by statute.” But the Court indicated that, if Congress wishes to incorporate a rule from the law of nations, that precedent must be “plain and unambiguous” in international law. Conspiracy was not. The opinion left open the question of Congress’s power to define expressly on its own an offense like conspiracy as an offense against the law of nations.

A number of federal circuit courts have been drawn into discussion of the allowable breadth of the Offenses Against the Law of Nations Clause, with differing conclusions. In 1980, Congress passed the Maritime Drug Law Enforcement Act (MDLEA). The law proscribes various drugrelated offenses on board any vessel within the jurisdiction of the United States or any vessel if the individual is a citizen or resident alien of the United States. In United States v. Davis (9th Cir. 1990), the Ninth Circuit Court of Appeals found that Congress intended to give extraterritorial effect to the act under its power to define “piracies and felonies on the high seas.”

In United States v. Martinez-Hidalgo (3d Cir. 1993), the Third Circuit determined that, under Article I, Section 8, Clause 10, Congress could constitutionally criminalize drug trafficking on the high seas even when the offense had no nexus with the United States, because “the trafficking of narcotics is condemned universally by law-abiding nations,” which would only be relevant if the court was invoking the law of nations provision of the clause. Congress would not have such power, the court suggested, if the prohibited conduct “were generally lawful throughout the world.” 

In United States v. Bellaizac-Hurtado (11th Cir. 2012), however, the Eleventh Circuit went further. Differing from other circuits, it found that drug trafficking was not an offense against the law of nations either at the founding or at the present time. The clause limits Congress to defining only established offenses under the law of nations, which the court defined as “customary international law.” The court declared, “The power to ‘define’ offenses against the law of nations does not grant Congress the authority to punish conduct that is not a violation of the law of nations.”

Hamdan and Bellaizac-Hurtado represent the first times that acts of Congress were struck down as exceeding the law of nations provision. And with Sosa opening the door, albeit narrowly, to federal common law based on the customary international law, it is reasonable to expect more challenges to Congress’s ability to define the law of nations based on the court’s interpretation of customary international law.

The clause permits Congress not only to establish criminal sanctions but civil legislation as well. In any event, like the other delegated grants of power to Congress, the clause defining Offenses Against the Law of Nations is limited by other “constitutional limitations,” ex parte Quirin, such as the First Amendment’s free speech guarantees. Boos v. Barry (1988).

Lastly, an additional question raised by scholars is whether the clause grants Congress power to define offenses and prescribe remedies for violation of the rights of individuals, or whether it also allows Congress to “punish” foreign states for their transgressions of international law. The latter interpretation bears upon the relative war and foreign affairs powers of Congress and the President.