The United States v. Zebulon Cantril was a Supreme Court case in which the defendant, Zebulon Cantril, had been convicted of violating an act of Congress that prohibited trading with the enemy during wartime. The issue before the court was whether or not this act applied to citizens who were living within enemy territory at the time and thus subject to their laws. The Supreme Court held that it did apply and affirmed Cantril's conviction on all counts. In its opinion, Chief Justice John Marshall wrote that "the power over commerce is vested in Congress by express words; and if it be competent for them to regulate commerce with foreign nations, they may certainly prohibit any intercourse between their own citizens and those nations." This ruling established a precedent whereby individuals could be prosecuted under federal law even when residing outside U.S borders but still considered part of American jurisdiction due to citizenship status or other factors such as allegiance owed to America through treaty obligations or military service abroad.

In United States v. Zebulon Cantril, the Supreme Court was asked to decide whether a federal court had jurisdiction over an action for trespass brought by the United States against Zebulon Cantril. The majority opinion held that it did not have such jurisdiction because the case involved only private rights and no public wrongs were alleged or proved. However, Justice Story dissented from this decision and argued that Congress had given federal courts exclusive original cognizance of all civil causes of admiralty and maritime jurisdiction as well as those arising under any act of Congress relating to revenue or other matters within their power. He further noted that while there may be some doubt about whether this particular case fell within these categories, he believed it should at least be heard in order to determine if there was a cause for relief on behalf of the government since they were seeking damages due to an alleged trespass committed by Cantril upon property owned by them. Therefore, Justice Story concluded that even though he could not agree with his colleagues' conclusion regarding lack of jurisdiction in this instance, he felt compelled to dissent from their opinion so as not allow any doubts concerning its correctness remain unresolved without being fully considered before judgment is rendered in favor of either party