Hostis humani generis

From the occasional regard during the age of Queen Elizabeth, of privateers and buccaneers as 'heroic' gentlemen adventurers of 'shrewd' mercantil venturers, piracy is now considered an offense of universal jurisdiction, such that any state may board and seize a ship engaged in piracy, and any state may try a pirate and impose sanctions according to that state's own law. Piracy is defined in article 101 of the 1982 Convention on the Law of the Sea, and the 1958 Convention on the High Seas also regulates this exercise of jurisdiction.
Sarah Barringer on Enemies of Mankind: The Image of Pirates in 18th-Century England, walk us through how Admiralty Law, before public international law, held maritime pirates —some of whom were in spite of their cruelty,  formidable navigators— and slavers to be beyond legal protection, and ready to be dealt with by any nation, even if that nation had not been directly attacked.