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).[94]
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;
In English admiralty law, piracy was defined as petit treason during the medieval period, and offenders were accordingly liable to be drawn and quartered on conviction. Piracy was redefined as a felony during the reign of Henry VIII. In either case, piracy cases were cognizable in the courts of the Lord High Admiral. English admiralty vice-admiralty judges emphasized that "neither Faith nor Oath is to be kept" with pirates; i.e. contracts with pirates and oaths sworn to them were not legally binding. Pirates were legally subject to summary execution by their captors if captured in battle. In practice, instances of summary justice and annulment of oaths and contracts involving pirates do not appear to have been common.
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).[95]