The need to strengthen the national government to protect against piracy and avoid the then current situation of each of the thirteen states treating the offense of piracy differently was an issue for the United States at the time of the Founding. For millennia, pirates have been referred to as hosts humanitarian's generis---"enemies of all humankind." Under the "law of nations," it was a crime of universal jurisdiction, but a state could choose only to enact proscriptions against various forms of "municipal or statutory piracy" that only applied within its jurisdiction. At the time of independence each of the new states enacted new piracy statues, but not each of them dealt with universal jurisdiction piracy. For example, Connecticut's statute only dealt with municipal piracy, while Pennsylvania's statute referenced the law of nations and, therefore, had universal jurisdiction. 

Under Article IX of the Articles of Confederation, congress had "the sole and exclusive right ... [and] States shall be restrained from...appointing courts for the trial of piracies and felonies committed on the high seas; and establishing courts for receiving and determining finally appeals in all cases of captures."

There were several problems with this provision. The Articles of Confederation did not set up a system of federal courts, so when Congress did pass an ordinance appointing courts under the piracy provision of the Articles, it provided that cases be tried by "the justices of the supreme or superior courts of judicature, and judge of the Court of Admiralty of the...states."

The other problem with the piracy provision under the Articles is that it allowed Congress to appoint courts but did not allow it to declare what was a piracy or other maritime felony. In fact, the ordinance Congress passed specifically allowed the states to use their own common law for the substantive crimes and causes of action to be brought against those accused of piracy. This allowed each of the states to prosecute piracy differently. And, as already stated, not all of the states' piracy statues had universal jurisdiction.

These problems were recognized immediately, but attempts at reform under the Articles proved impossible. Thus, at the Constitutional Convention, there was little discussion of the provision, for the delegates understood the difficulties that had beset the Confederation Congress. The delegates therefore accorded Congress the power to "define and punish Piracies and Felonies committed not he High Seas."

Almost immediately, in 1790, Congress undertook the task. It defined piracy as murder or robbery on the high seas, or any other crime committed on the high seas that would be punishable by death under United States law, if committed on land. In 1819, Congress passed the predecessor to the present-day piracy statute. It removed any nexus to the territory of the United States from the definition of piracy and instead conceived of piracy as a truly universal crime defined by the law of nations. The current piracy statute, enacted in 1909 and based on the 1819 statutes, can be found in 18 U.S.C. § 1651: "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." 

The reference to the "law of nations" in section 1651 was subject to a constitutional challenge in 1820. In United States v. Smith (1820), Justice Joseph Story opined that the crime of piracy had a definite meaning in international law, and that consequently, Congress's definition of piracy was sufficiently precise. Justice Story also concluded that the crime of piracy under the law of nations consisted of acts of robbery at sea.

No additional piracy cases have been litigated before the Supreme Court since 1820. However, piracy cases may end up before the Supreme Court int he near future, in light of recent controversy over the definition of piracy. While the first Supreme Court case limited the crime of piracy to robbery on the high seas, more recently, the courts have expanded the definition of piracy in light of contemporary customary international law.

In 2010, two new piracy cases litigated in federal courts raised novel issues regarding the definition of piracy. United States v. Said (2010), involved the pirates who approached a U.S. ship on a small skiff. Although one of the pirates fired a shot at the ship, no pirates boarded or attempted to board it. Instead, pirates were apprehended by the crew of the ship and subsequently taken to Virginia for a criminal prosecution. the pirates moved for dismissal of the count of piracy against them, alleging that their acts did not constitute piracy under section 1651 because they did not board or take control of the victim vessel. The district court granted the motion to dismiss, concluding that the definition of "piracy" in the 1820 Supreme Court Smith case as "robbery or forcible depredations committed upon the sea" was still valid, and that due process considerations did not allow a construction of the piracy statute to include other actions. The court, in effect, decided that attempted piracy was not a crime under the law of nations, either in 1820 or today. 

In the second case, United States v. Hansan (2010), pirates mistook a military vessel, the U.S.S. Nicholas, for a merchant ship. After an initial exchange of fire between the pirates and the crew of the U.S.S. Nicholas, the pirates fled in their vessel but were captured and brought to the United States for prosecution. These pirates similarly moved for dismissal of the piracy count under section 1651, arguing that the facts in the indictment were insufficient to constitute the crime of piracy. The court denied the motion, concluding that in light of developments in American piracy law, and of more recently drafted international treaties and customary law, piracy must be defined according to "contemporary customary international law." the court found that customary international law had evolved on the subject of maritime piracy and had changed since 1820 when the United States Supreme Court decided the Smith case. Finally, the court concluded that contemporary customary international law did not require an actual robbery on the high seas as a prerequisite for a piracy conviction under section 1651. 

The defendants in the Hasan case appealed their conviction and sentence of life imprisonment to the Fourth Circuit court of Appeals. The Fourth Circuit affirmed the conviction in United States v. Dire (2012) and vacated the decision in Said. The appellate judges concluded that when Congress enacted section 1651 and provided for piracy to be defined by the "law of nations," it had contemplated that the definition of piracy would evolve as the law of nations evolved. The Fourth Circuit thus opined that limiting the definition of piracy to robbery on the high seas would "render it incongruous with the modern law of nations and prevent [the federal courts] from exercising universal jurisdiction in piracy cases."

In a third case, United States v. Shibin (2012), pirates attacked and hijacked a German vessel and a United States yacht. The defendant was not directly involve din the attack; rather, he subsequently served as a hostage negotiator for the pirates and received a share of the ransom money. He was convicted under section 1651 and sentenced to life imprisonment. The district court, as in the Hasan case, opined that the crime of piracy under section 1651 encompassed acts other than just robbery at sea. At this writing, the case is pending appeal.

Finally, in United States v. Ali (2012), the d.c. District Court held that universal jurisdiction over the crime of piracy did not extend to the crime of conspiracy to commit piracy. This was the first case in United States history in which the government asserted universal jurisdiction over a crime of piracy had no connection to the United States or its citizens. The defendant in Ali allegedly assisted the pirates both before and after their crime. He, in fact, provided interpretation services after the hostages were already in the pirates' custody in order to negotiate their ransom. One of the counts that the defendant was charged with included conspiracy to commit piracy. The court reasoned that because of the exceptional nature of universal jurisdiction, federal courts could only rely upon it when the precise conduct in question was not universally cognizable. Moreover, the court held that universal jurisdiction over piracy only applied on the high seas and not in foreign countries. It concluded that the universal jurisdiction over piracy included acts that aided or abetted the crime, but not conspiracy to commit the crime. Under this view, pirate negotiators have a form of immunity when acting on behalf of (and aiding and abetting for profit) those pirates who actually board the vessel. 

In U.S. federal courts today, piracy now includes acts committed on the high seas other than robbery. It is thus likely that an unsuccessful attempt to rob a ship on the high seas would fall under the statute.