The United States v. The Brig Eliza was a Supreme Court case in which the court had to decide whether or not the capture of a vessel by an American privateer during wartime constituted as piracy. At issue was whether or not the brig Eliza, owned by British subjects and captured while sailing from Jamaica to London, could be considered a lawful prize of war under international law. After hearing arguments from both sides, Chief Justice John Marshall delivered his opinion that since there were no hostilities between Britain and America at the time of capture, it did constitute piracy according to international law and therefore must be returned with damages paid for its detention. This decision set an important precedent regarding how captures made during times when two countries are not officially at war should be treated under maritime law.

In The United States v. The Brig Eliza, the Supreme Court was asked to decide whether a vessel that had been captured by an American privateer during the War of 1812 could be considered a lawful prize and sold for profit. Justice Story delivered the dissenting opinion in which he argued that since Congress had not declared war against Great Britain at the time of capture, it would be improper to consider this vessel as a lawful prize. He reasoned that while Congress may have authorized hostilities against British vessels, they did not authorize any captures or seizures until after war was officially declared on June 18th, 1812. Therefore, according to Justice Story's dissent, all captures made prior to this date were unlawful and should not be allowed under international law or U.S domestic law because such acts are tantamount to piracy rather than legitimate warfare activities sanctioned by government authority.