The Mayor, Aldermen and Inhabitants of New Orleans appealed to the United States Supreme Court in a case concerning whether or not the federal government had authority over state governments. The city argued that Congress did not have power to regulate commerce within states, as they believed it was an issue for individual states to decide. The United States countered by asserting that Congress had the right under its constitutional powers to pass laws regulating commerce between different states and with foreign nations. Ultimately, the court ruled in favor of the federal government's position; finding that Congress has broad authority over interstate commerce and can enact legislation related thereto without interference from state governments. This decision established a precedent which has been used ever since when determining if certain actions are permissible under Congressional power or must be left up to individual states' discretion.

In The Mayor, Aldermen and Inhabitants of New Orleans v. The United States, the Supreme Court was asked to decide whether a state could be sued in federal court without its consent. The majority opinion held that states were not immune from suit in federal courts; however, Justice McLean dissented on this point. He argued that the Constitution did not grant Congress power to authorize suits against non-consenting states and thus such suits should be barred by the Eleventh Amendment. Furthermore, he maintained that allowing such lawsuits would violate principles of comity between sovereigns as well as undermine state sovereignty by subjecting them to judgments they had no part in making or approving. Ultimately, Justice McLean concluded that it was up to each individual state legislature to determine if their respective governments could be sued in federal court without their consent and until then any attempts at doing so should remain prohibited under the Eleventh Amendment.