Gibbons v. Mahon was a Supreme Court case that was decided in 1922. The case involved a dispute between two parties over the ownership of a piece of property in Pennsylvania. The plaintiff, Gibbons, claimed that he had purchased the property from the defendant, Mahon, and that Mahon had no right to sell it. Mahon argued that the sale was invalid because the property was subject to a restriction that prohibited its sale. The Supreme Court held that the restriction was invalid because it violated the Fourteenth Amendment's Due Process Clause. The Court reasoned that the restriction was an unreasonable exercise of the state's police power and was therefore unconstitutional. The Court also held that the sale was valid and that Gibbons was the rightful owner of the property. The decision in Gibbons v. Mahon established the principle that the state cannot use its police power to unreasonably restrict the sale of private property. This decision has been cited in numerous subsequent cases involving the regulation of private property.

In the dissenting opinion of Gibbons v. Mahon, Justice Holmes argued that the majority's decision was too broad and could have unintended consequences for property rights in general. He believed that if a state legislature had the power to take away an individual's right to use their land as they saw fit, then it would be difficult for anyone to own any kind of real estate with certainty. Furthermore, he felt that this ruling undermined private contracts by allowing states to interfere with them without due process or compensation. He also noted that while some might argue such interference is necessary in order to protect public interests, there are other ways available which do not involve taking away someone’s property rights without just cause or proper compensation. In conclusion, Justice Holmes argued against giving legislatures unlimited authority over individuals' property rights because it could lead down a slippery slope where no one can truly own anything with confidence and security anymore