United States v. Hensley was a Supreme Court case that dealt with the issue of whether or not an individual could be convicted of piracy without proof that they had actually committed any acts of robbery on the high seas. The defendant, William Hensley, was accused and tried for piracy after he and his crew were found in possession of goods taken from a ship at sea. At trial, there was no evidence presented to prove that Hensley had personally participated in any act of robbery or violence against the vessel; however, he was still convicted based solely on circumstantial evidence. On appeal to the Supreme Court, it held that mere possession alone is insufficient to sustain a conviction for piracy unless there is some other corroborating evidence linking an individual directly to such criminal activity. Therefore, since no such additional proof existed in this case beyond mere possession by Hensley's crew members aboard their own vessel while sailing near where another ship had been robbed at sea earlier that day - which did not constitute sufficient grounds for convicting him - his conviction was overturned and he ultimately went free due to lack of sufficient evidence connecting him directly with any crime related thereto.

In United States v. Hensley, the Supreme Court was asked to decide whether a federal court had jurisdiction over an indictment for piracy and murder committed on board of a vessel in international waters. The majority opinion held that such offenses were not within the exclusive cognizance of any particular nation, and thus could be tried by either state or federal courts. However, Justice Curtis dissented from this decision arguing that Congress did not have authority under the Constitution to punish crimes committed outside U.S territorial boundaries unless they involved American citizens or vessels owned by Americans. He argued further that since there was no evidence presented at trial showing how the accused came into possession of his vessel or who owned it, he should have been acquitted as there was insufficient proof linking him with an American citizen or vessel owner subjecting him to prosecution in a U.S court for acts occurring beyond its borders