Hostis humani generis

Hostis humani generis (Latin for 'an enemy of mankind') is a legal term of art that originates in admiralty law. Before the adoption of public international law, pirates and slavers were already held to be beyond legal protection and so could be dealt with by any nation, even one that had not been directly attacked. A comparison can be made between this concept and the common law "writ of outlawry", which declared a person outside the king's law, a literal out-law, subject to violence and execution by anyone. The ancient Roman civil law concept of proscription, and the status of homo sacer conveyed by proscription may also be similar. Perhaps the oldest of the laws of the sea is the prohibition of piracy, as the peril of being set upon by pirates, who are not motivated by national allegiance, is shared by the vessels and mariners of all nations, and thus represents a crime upon all nations. Since classical antiquity, pirates have been held to be individuals waging private warfare, a private campaign of sack and pillage, against not only their victims, but against all nations, and thus, those engaging in piracy hold the particular status of being regarded as hostis humani generis, the enemy of humanity. Since piracy anywhere is a peril to every mariner and ship everywhere, it is held to be the universal right and the universal duty of all nations, regardless of whether their ships have been beset by the particular band of pirates in question, to capture, try by a regularly constituted court-martial or admiralty court (in extreme circumstances, by means of a drumhead court-martial convened by the officers of the capturing ship), and, if found guilty, to execute the pirate via means of hanging from the yard-arm of the capturing ship, an authoritative custom of the sea. Although summary battlefield punishment was conducted by certain nations at certain times with regard to pirates, it was regarded as irregular (but lawful if the attenuation of due process was dictated by urgent military necessity), as individuals captured with pirates could potentially have a defense to charges of piracy, such as coercion.