U.S. Constitution · Article I, Section 8, Clause 10

Define and Punish Clause

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Also known as: Define and Punish Clause

The Define and Punish Clause grants Congress the power to define and punish piracy, felonies on the high seas, and offenses against the law of nations, forming a key part of federal authority over foreign relations and maritime conduct.

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Cited in 2 SI Solutions and 10 grades this month.

26 public items cite this provision · 12 in October 2026 (last month: 1)

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Citations per week, last 12 weeks

The text

To define and punish Piracies and Felonies committed on the high Seas, and Offences against the Law of Nations;

National Archives transcription (public domain; original spelling and capitalization). archives.gov

SI explainer

What it means

This clause gives Congress the power to define and punish three categories of wrongdoing: piracy, felonies committed on the high seas, and offenses against the law of nations. The first category, piracy, refers to robbery or other violent acts committed at sea by private individuals against other ships. The second, felonies on the high seas, covers serious crimes that occur in international waters, beyond the jurisdiction of any single country. The third, offenses against the law of nations, refers to violations of customary international law, such as mistreatment of ambassadors or other acts that could draw the nation into conflict with foreign powers. The clause is an enumerated power, meaning it lists a specific area where Congress can legislate. It does not require the states to act, and it gives Congress the authority to define these crimes, not just punish them. This means Congress can specify what constitutes piracy or an offense against the law of nations, and then set penalties. The power is not unlimited; it applies only to the three categories listed. For example, it does not cover crimes on land or within a state's territory, unless they are connected to the high seas or the law of nations. Later amendments have not changed this clause directly, but the Supreme Court has interpreted its scope in cases involving military commissions and the law of war. In Ex parte Quirin (1942), the Court upheld the trial of Nazi saboteurs by military commission for violations of the law of war, which is related to offenses against the law of nations. In Hamdan v. Rumsfeld (2006), the Court held that military commissions set up to try Guantanamo detainees were not authorized by Congress and violated the Uniform Code of Military Justice and Common Article 3 of the Geneva Conventions. These cases show that the clause's reach into military justice and international law remains a subject of judicial interpretation.

Original meaning

To the founding generation, this clause was a practical and essential part of creating a national government that could act as one nation in foreign affairs. James Madison, writing in The Federalist No. 42, grouped this power with other foreign relations powers, noting that it was an 'obvious and essential branch of the federal administration.' He argued that 'if we are to be one nation in any respect, it clearly ought to be in respect to other nations.' This suggests that the clause was intended to give the federal government the authority to deal with international crimes that could affect the nation's standing and relations with other countries. The original meaning also reflects the need to address piracy, which was a serious threat to trade and security in the late 18th century. The clause allowed Congress to define piracy and felonies on the high seas, ensuring that there was a uniform federal law to punish such crimes, rather than leaving it to individual states. The reference to the law of nations was understood to include customary international law, such as the protection of ambassadors and the rules of war. The founders likely intended this clause to enable the United States to fulfill its obligations under international law and to avoid conflicts with other nations.
  • “to define and punish piracies and felonies committed on the high seas, and offenses against the law of nations; to regulate foreign commerce, including a power to prohibit, after the year 1808, the importation of slaves, and to lay an intermediate duty of ten dollars per head, as a discouragement to such importations.” James Madison, The Federalist No. 42 (1788-01-22)
  • “This class of powers forms an obvious and essential branch of the federal administration.” James Madison, The Federalist No. 42 (1788-01-22)
  • “If we are to be one nation in any respect, it clearly ought to be in respect to other nations.” James Madison, The Federalist No. 42 (1788-01-22)

How the Supreme Court has read it

  1. Ex parte Quirin, 317 U.S. 1 (1942)

    The Court upheld the trial of Nazi saboteurs, including one claimed U.S. citizen, by military commission for violations of the law of war, indicating that offenses against the law of nations can include war crimes and that Congress has authority to define and punish such offenses.

  2. Hamdan v. Rumsfeld, 548 U.S. 557 (2006)

    The Court held that military commissions convened to try Guantanamo detainees were not authorized by Congress and violated the Uniform Code of Military Justice and Common Article 3 of the Geneva Conventions, limiting the executive's power to define and punish offenses against the law of nations without congressional authorization.

Two schools of interpretation

Originalist / textualist reading

Originalists and textualists read this clause as a specific grant of power to Congress, limited to the three categories listed. They emphasize that the words 'define' and 'punish' give Congress the authority to create federal crimes in these areas, but only for piracy, felonies on the high seas, and offenses against the law of nations. They argue that the original public meaning of 'law of nations' referred to the customary international law of the time, which included rules on ambassadors, treaties, and the conduct of war. Originalists would likely view the clause as authorizing Congress to legislate on these matters, but not to expand it to cover new areas without a constitutional amendment. They would also stress that the clause is an enumerated power, meaning it should be interpreted narrowly, and that any ambiguity should be resolved in favor of limiting federal power.

Living-constitutionalist reading

Living constitutionalists and pragmatists read this clause as a flexible grant of power that allows Congress to adapt to changing circumstances in international law and global affairs. They argue that the phrase 'offenses against the law of nations' is dynamic, evolving as international law develops, so Congress can define new offenses that reflect modern standards, such as terrorism or cybercrimes. They would point to the Supreme Court's decisions in Ex parte Quirin and Hamdan v. Rumsfeld as examples of how the clause interacts with the executive's war powers and international obligations. Living constitutionalists would emphasize that the clause's purpose is to enable the United States to act as a responsible member of the international community, and that a rigid interpretation would hinder the nation's ability to address new threats. They would also note that the clause is part of a broader framework of federal powers that must be interpreted in light of contemporary needs and values.

Open questions

The scope of 'offenses against the law of nations' remains unsettled, particularly whether it includes modern international crimes like terrorism or cyberattacks. The relationship between this clause and the President's war powers, especially regarding military commissions, is also a subject of ongoing debate.

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Values for America Constitution Explorer, https://www.valuesforamerica.com/constitution (text: National Archives transcription, public domain), Article I, Section 8, Clause 10, https://www.valuesforamerica.com/constitution/article-1/section-8/clause-10

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