Swain v. Seamens was a United States Supreme Court case that was decided in 1869. The case involved a dispute between a ship captain and a sailor over wages. The sailor, Seamens, had signed a contract with the captain, Swain, to work on a voyage from New York to San Francisco. Seamens was promised a certain amount of wages for the voyage, but when the voyage was completed, Swain refused to pay Seamens the full amount of wages that he was owed. Seamens sued Swain in a federal court, claiming that he was entitled to the full amount of wages that he was promised. The court ruled in favor of Seamens, and Swain appealed the decision to the Supreme Court. The Supreme Court affirmed the lower court's ruling, finding that Seamens was entitled to the full amount of wages that he was promised. The Court held that a contract between a ship captain and a sailor was binding, and that the captain was obligated to pay the sailor the full amount of wages that he was promised. This ruling established a precedent that contracts between ship captains and sailors were binding and enforceable.

In the case of Swain v. Seamens, Chief Justice Chase delivered a dissenting opinion in which he argued that Congress had no authority to pass laws regulating seamen's wages and contracts. He stated that such matters were traditionally left to state law and should remain so. Furthermore, he argued that if Congress did have the power to regulate these matters, it would be an unconstitutional exercise of its powers under the Commerce Clause because it would interfere with states' rights over their own internal affairs. Finally, Chief Justice Chase noted that even if Congress did have this power, there was nothing in the Constitution or any other federal statute granting them such authority in this particular case.