Barton v. Petit and Bayard was a case heard by the United States Supreme Court in 1813. The dispute arose from an agreement between Barton, a merchant of Baltimore, and Petit and Bayard, two merchants of Philadelphia. Under the terms of their contract, Barton agreed to deliver goods to them at certain times for which he would be paid in installments over several months. When payment was not made as promised on time, Barton sued for breach of contract but lost his case before the Circuit Court due to lack of evidence that he had fulfilled all conditions required under the agreement. On appeal to the Supreme Court however, Chief Justice John Marshall reversed this decision ruling that even though there may have been some minor discrepancies with regards to delivery dates or other details mentioned in their contract; these were not sufficient enough grounds for denying him compensation since it could be proven that he had delivered most if not all goods as per their agreement thus entitling him damages accordingly.

In Barton v. Petit and Bayard, the Supreme Court was asked to decide whether a state court had jurisdiction over a case involving citizens of two different states. The majority opinion held that the state court did not have jurisdiction because it violated Article III of the Constitution which grants federal courts exclusive jurisdiction in such cases. Justice Johnson dissented from this decision, arguing that there is nothing in Article III or any other part of the Constitution which prevents a state court from exercising its own authority when both parties are citizens of different states. He argued further that if Congress had intended for only federal courts to hear such cases then they would have explicitly stated so in either Article III or some other part of the Constitution. Therefore, he concluded that since no such language exists then it must be assumed that Congress left these matters up to individual states and their respective laws regarding judicial power and procedure.