By definition, a pirate is any person committing a criminal acts against public authority, on the high seas outside the normal jurisdiction and laws of any state (country). By law, they can be arrested, prosecuted, and sentenced by any state that captures them. Also, by definition, the criminal act is of a private nature, that is personal gain, and not for political reasons.
The end of the 17th century saw the greatest outburst of piracy in the history of seafaring. Ironically called 'the Golden Age of Piracy', the era lasted for around 30 years, from around 1700-1730. Although the most troubled area was the Caribbean, piracy was also rife off the Eastern seaboard of America, in the Indian Ocean and off the West Coast of Africa (where the 'Pirate Round' followed the trade routes from India to America via Africa). The piracy boom was the result of circumstances: the end of the War of the Spanish Succession (between France and an Alliance of England, Holland and the German States) meant that ports were full of unemployed sailors and there was a general lack of legal employment. The majority of the pirates who have gripped the popular imagination operated during this period.