letter of marque

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A letter of marque is a government license authorizing the bearer to engage in privateering. Holders of these commissions were entitled to outfit private warships for the purposes of sinking or capturing vessels belonging to enemy nations. Ships captured by these privateers were subject to prize law

Congress has exclusive power to grant letters of marque pursuant to Article I, § 8, clause 11 of the Constitution. However, Congress has not exercised this power in over two-hundred years. 

Letters of Marque in Context

During the Age of Sail, letters of marque were a popular and cost-effective method for governments to disrupt an enemy nation’s economy. Privateering ships cost the state nothing, and the wealth they captured from hostile nations could help fund a state’s war effort. 

Privateering played a major role in early American history. During the Revolutionary War, letters of marque were given to armed merchant vessels and dedicated privateering ships alike. These commissions were issued on a per-voyage basis by the Continental Congress and state governments. The contributions these ships made in America’s independence movement is among the reasons why issuing letters of marque became an enumerated power of Congress.  

Although letters of marque only authorized the holder to attack ships belonging to hostile nations, many privateers also engaged in piracy, attacking neutral and allied shipping. This opportunism was especially common when peace broke out and privateers were expected to return to normal commerce. 

Privateering saw a decline in use in the mid-nineteenth century. The decline culminated in the Paris Declaration respecting Maritime Law of 1856, which formally banned the practice. Although the United States is not a signatory to the agreement, it has declared it would respect the principals laid out in the treaty. The United States has not since issued letters of marque, although they retain the legal power to do so. 

[Last updated in June of 2023 by the Wex Definitions Team]