I have heard that it wasn’t uncommon for pirates to buy goods from merchants, and merchants making secretive deals with pirates to sell their goods.
Weren’t merchants and their vessels part of their country’s navy in some sense? If so, didn’t they have to list who and where they sold their goods to? (If a pirate or an unexpected buyer was on the list, wouldn’t a merchant captain get in trouble for it?)
Was it always the merchant captains who agreed to secretly sell their goods to pirates? Or would part of the crew sometimes do it behind their backs?
An interesting question, I hope my answer can do it justice.
The simplest way for merchants to trade with pirates was simply to not declare it or to 'cook the books'. Much of the illicit trade with pirates occurred in the colonies where the demand for consumer goods often outweighed the scruples of the customers, and sometimes the very officials charged with policing trade were guilty of collusion. Ellis Brand, RN captain of HMS Lyme, for example, wrote that Virginia Collector of Customs Richard Fitzwilliams acted as an ‘agent and soliciter for the Pirats in those parts’, going so far as to have a writ taken out against Captain Pearse of HMS Phoenix and having Captain Gordon of HMS Pearl arrested for false imprisonment. For a fee of three ounces of gold dust, Blackbeard’s quartermaster, William Howard, retained Fitzwilliams’ services as a lawyer. Pirates were assisted in North Carolina by Tobias Knight, Collector of Customs, Council member, Secretary to the Colony, and former Chief Justice. In a letter to the pirates, Knight described himself as Blackbeard’s ‘real ffriend [sic] and Servant’, and his services to the pirates included not only obstructing Brand’s investigations, but also storing and concealing stolen sugar and cotton in his own barn.
However, such illicit trade occurred all over the globe, in Africa, the Indian Ocean, and even in England itself. Probably the most successful pirate trading enterprise was that of Frederick Philipse, who sent Adam Baldridge as a factor to St. Mary's Island, Madagascar, where he ran a trading post supplying pirates with 'Western' commodities alongside a legitimate slave business, allowing Philipse to easily mask the source of his income. On occasion Philipse also smuggled pirated commodities into New York to escape the customs.
More info and sources in pp. 161-172 of my DOCTORAL THESIS