Being privately owned and run, privateers did not take orders from the Naval command. The letter of marque of a privateer would typically limit activity to a specific area and to the ships of specific nations. Typically, the owners or captain would be required to post a performance bond against breaching these conditions, or they might be liable to pay damages to an injured party. In the United Kingdom, letters of marque were revoked for various offences.
Conditions on board privateers varied widely. Some crews were treated as harshly as naval crews of the time, while others followed the comparatively relaxed rules of merchant ships. Some crews were made up of professional merchant seamen, others of pirates, debtors, and convicts.
Some privateers ended up becoming pirates, not just in the eyes of their enemies but also of their own nations. William Kidd, for instance, began as a legitimate British privateer but was later hanged for piracy.
The Paris Declaration Respecting Maritime Law of 16 April 1856 was issued to abolish privateering. It regulated the relationship between neutral and belligerent and shipping on the high seas introducing new.
England, and later the United Kingdom, used privateers to great effect and suffered much from other nations' privateering. During the 15th century, "piracy became an increasing problem and merchant communities such as Bristol began to resort to self-help, arming and equipping ships at their own expense to protect commerce." These privately owned merchant ships, licensed by the crown, could legitimately take vessels that were deemed pirates. This constituted a "revolution in naval strategy" and helped fill the need for protection that the current administration was unable to provide as it "lacked an institutional structure and coordinated finance."
The increase in competition for crews on armed merchant vessels and privateers was due, in a large part, because of the chance for a considerable payoff. "Whereas a seaman who shipped on a naval vessel was paid a wage and provided with victuals, the mariner on a merchantman or privateer was paid with an agreed share of the takings."This proved to be a far more attractive prospect and privateering flourished as a result.
During Queen Elizabeth's reign, she "encouraged the development of this supplementary navy." Over the course of her rule, she had "allowed Anglo-Spanish relations to deteriorate" to the point where one could argue that a war with the Spanish was inevitable. By using privateers, if the Spanish were to take offense at the plundering of their ships.
Queen Elizabeth could always deny she had anything to do with the actions of such independents. Some of the most famous privateers that later fought in the Anglo-Spanish War (1585–1604) included the Sea Dogs.(wikipedia.org)