Summary of Pennsylvania Coal v. Mahon, S. Ct 260 US 393 
Relevant Facts: Df Mahon purchased a house and property minus the right to mine coal beneath by deed. PA passed a statute forbidding the mining of coal in a manner such to cause subsidence to any structure used for human habitation or where such was located w/i 150 ft of the mine.
Legal Issue(s): Whether statute forbidding any mining of coal that would cause the subsidence of any house, unless the house was the property of the owner of the coal and was more than 150 ft from the improved property of another was a legitimate exercise of police power?
Court’s Holding: NO
Procedure: Tr Ct held statute unconstitutional judgment for Df; S. Ct PA reversed; S. Ct Reversed.
Law or Rule(s): Under the 5th Amendment, private property that is wanted for public use shall not be taken w/o just compensation. Property may be regulated to a certain extent, but if regulation goes too far it will be recognized as a taking.
Court Rationale: Govt could hardly go on if to some extent values incident to property could not be diminished w/o paying for every such change in the general law. Some values are enjoyed under an implied limitation and must yield to the police power. In determining such limits, the extent of diminution must be considered. When it reaches a certain magnitude there must be an exercise of eminent domain and compensation to sustain the act. A source of damage to single house is not a public nuisance even if similar damage is inflicted on others in different places. The damage is not common or public. The statute is not justified for the protection of personal safety. The df gave timely notice of intent to mine under the house. The extent of the taking is great, it seeks to abolish an estate in land, a valuable estate. So far as private persons or communities have seen fit to take the risk of acquiring only surface rights, we cannot see that the fact that their risk has become a danger warrants giving them greater rights than they bought.
Plaintiff’s Argument: The statute forbids mining of coal which would cause the subsidence of the Pl’s house on the surface and is a legitimate exercise of police powers in protecting the safety of the public.
Defendant’s Argument: The statute would effectively destroy the Df’s rights that it retained under the K for the sale of property, and if valid would constitute a taking.
DISSENT: The State does not appropriate the property or make any use from it, the state merely seeks to prevent the owner from making a use which interferes with paramount rights of the public. A restriction upon use cannot be lawfully imposed unless its purpose is to protect the public as an appropriate means to the public end.