
Definition:
The privateers acted on a commission recognised under the Law of Nations.
One of the principle clauses of a letter of marque is that of specifically naming
the country whose vessels can be legally captured. There were heavy penalties if
the property of other nations was violated.
Letters of Marque did not completely safeguard a privateer from prosecution even
when ships of certain countries were excluded from attacks. When a privateer is
captured by hostile nations he is often charged with being a pirate and swiftly
executed. Also when countries make peace between them and a privateer fails to
get the news about this in time he can be prosecuted if he continues to attack
ships of the now friendly nation. Sometimes a privateer is such a long time away
from home or the colonies that he only hears the news of a peace treaty when he
returns home from his privateering enterprise.
The use of Letters of Marque was discontinued by many countries who signed the Declaration of Paris in 1856. The United States as well as several other countries signed the International Treaty much later. The US was at that time much more dependent on their use to increase their Maritime power because they lacked a Large Navy.