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In the United States, criminal prosecution of piracy is authorized in the U.S. Constitution, Art. I Sec. 8 cl. 10:

The Congress shall have Power … To define and punish Piracies and Felonies committed on the high Seas, and Offences against the Law of Nations;

Title 18 U.S.C. § 1651 states:

Whoever, on the high seas, commits the crime of piracy as defined by the law of nations, and is afterwards brought into or found in the United States, shall be imprisoned for life.

Law of nations

Piracy is of note in international law as it is commonly held to represent the earliest invocation of the concept of universal jurisdiction. The crime of piracy is considered a breach of jus cogens, a conventional peremptory international norm that states must uphold. Those committing thefts on the high seas, inhibiting trade, and endangering maritime communication are considered by sovereign states to be hostis humani generis (enemies of humanity).[115]

For a different opinion on Pirates as Hostis Humani Generis see Caninas, Osvaldo Peçanha. Modern Maritime Piracy: History, Present Situation and Challenges to International Law. Paper presented at the annual meeting of the ISA – ABRI JOINT INTERNATIONAL MEETING, Pontifical Catholic University, Rio de Janeiro Campus (PUC-Rio), Rio de Janeiro, Brazil, Jul 22, 2009

In the United States, criminal prosecution of piracy is authorized in the U.S. Constitution, Art. I Sec. 8 cl. 10:

The Congress shall have Power … To define and punish Piracies and Felonies committed on the high Seas, and Offences against the Law of Nations;

Title 18 U.S.C. § 1651 states:

Whoever, on the high seas, commits the crime of piracy as defined by the law of nations, and is afterwards brought into or found in the United States, shall be imprisoned for life.

Citing the United States Supreme Court decision in the year 1820 case of United States v. Smith,[116] a U.S. District Court ruled in 2010 in the case of United States v. Said that the definition of piracy under section 1651 is confined to “robbery at sea.” The piracy charges (but not other serious federal charges) against the defendants in the Said case were dismissed by the Court.[117]

Since piracy often takes place outside the territorial waters of any state, the prosecution of pirates by sovereign states represents a complex legal situation. The prosecution of pirates on the high seas contravenes the conventional freedom of the high seas. However, because of universal jurisdiction, action can be taken against pirates without objection from the flag state of the pirate vessel. This represents an exception to the principle extra territorium jus dicenti impune non paretur (the judgment of one who is exceeding his territorial jurisdiction may be disobeyed with impunity).[118]
[edit] International conventions
[edit] UNCLOS Article 101: Definition

In the United Nations Convention on the Law of the Sea (UNCLOS) of 1982, “maritime piracy” consists of:

(a) any illegal acts of violence or detention, or any act of depredation, committed for private ends by the crew or the passengers of a private ship or a private aircraft, and directed:

(i) on the high seas, against another ship or aircraft, or against persons or property on board such ship or aircraft;
(ii) against a ship, aircraft, persons or property in a place outside the jurisdiction of any State;

(b) any act of voluntary participation in the operation of a ship or of an aircraft with knowledge of facts making it a pirate ship or aircraft;
(c) any act of inciting or of intentionally facilitating an act described in subparagraph (a) or (b).[119]

A limitation of UNCLOS Art 101 is that it confines piracy to the High Seas. As the majority of piratical acts occur within territorial waters, some pirates are able to go free as certain jurisdictions lack the resources to monitor their borders adequately.
[edit] IMB Definition

The International Maritime Bureau (IMB) defines piracy as:

the act of boarding any vessel with an intent to commit theft or any other crime, and with an intent or capacity to use force in furtherance of that act.[120]

[edit] Uniformity in Maritime Piracy Law

Given the diverging definitions of piracy in international and municipal legal systems, some authors argue that greater uniformity in the law is required in order to strengthen anti-piracy legal instruments.[121]