The Convoy's Wheat is a Supreme Court case from 1865 that dealt with the issue of whether or not a state could impose taxes on goods imported by sea. The plaintiff, William H. Seward, argued that such taxation was unconstitutional as it violated the Commerce Clause of the Constitution which gives Congress exclusive power to regulate interstate commerce. The court ultimately sided with Seward and held that states cannot tax goods imported by sea because this would be an interference in interstate commerce and thus violate the Commerce Clause. This decision established important precedent for future cases dealing with similar issues regarding taxation and interstate commerce, ensuring that only Congress has authority over these matters.

In The Convoy's Wheat, the Supreme Court was asked to decide whether a contract between two parties should be enforced even though it violated an act of Congress. A majority of the court held that contracts made in violation of acts of Congress are void and cannot be enforced. However, Justice Field dissented from this opinion and argued that while such contracts may not be enforceable under federal law, they can still remain valid under state law. He reasoned that since there is no express provision in the Constitution prohibiting states from recognizing these types of contracts, then they should have authority to do so if they choose. Furthermore, he argued that allowing states to recognize such agreements would promote commerce by providing certainty for those who enter into them as well as encouraging people to engage in business activities without fear or uncertainty about their legal rights or obligations.