Pennsylvania Coal Co. v. Mahon
The Court ruled that Pennsylvania's Kohler Act went too far in banning coal mining that could cause houses to sink, because it destroyed the coal company's property and contract rights without paying for them.
The decision established a lasting principle in American law: a government regulation that goes far enough in wiping out a property owner's value can count as a 'taking' requiring compensation, even without any physical seizure of land.
“The general rule at least is, that while property may be regulated to a certain extent, if regulation goes too far it will be recognized as a taking.”
The Court's foundational statement that regulation can become an unconstitutional taking.
How it got here: A Pennsylvania trial court refused an injunction, ruling the statute unconstitutional; the state supreme court reversed and upheld the law; the coal company brought a writ of error to the U.S. Supreme Court.
The Case in Depth
What happened
A coal company had sold surface land in 1878 while keeping the right to mine the coal underneath, with the buyer agreeing to accept the risk of the ground sinking. Decades later, Pennsylvania passed the Kohler Act, banning coal mining that would cause homes above to subside. The homeowners sued to stop the company from mining under their house.
The question before the Court
Could Pennsylvania stop a coal company from mining coal it had reserved the right to mine, just because it might cause a house above to sink, without paying the company for its loss?
Why it matters
This case gave property owners a constitutional tool to challenge regulations that destroy the value of their land or resources, even when the government never physically takes anything. It shaped how courts everywhere evaluate zoning laws, environmental rules, and other regulations that limit what owners can do with their property.
What changes now
The Pennsylvania Supreme Court's decree enforcing the Kohler Act against the coal company was reversed, meaning the company could proceed with mining under the house. Because the Court addressed the law's general validity, not just this one property, its reasoning was understood to bar enforcement of the Act's core restriction more broadly wherever coal-mining rights had been reserved by contract. This is a final merits decision, not a temporary order.
Concurrences and dissents
Dissent — Justice Brandeis
“But restriction imposed to protect the public health, safety or morals from dangers threatened is not a taking.”Brandeis's argument that a safety-based restriction is not the same as a government taking.
Justice Brandeis argued the Kohler Act was simply a valid ban on a 'noxious use' of property to prevent public harm, not a taking, because the company kept possession of its coal and the state took nothing for itself. He said value should be judged against the whole property, not just the coal affected, and that reciprocal advantage between owner and public isn't required when the goal is preventing danger rather than conferring a mutual benefit.
How the Court got there
The legal reasoning, step by step
- The Court explained that property regulation is normally allowed because some property values are always understood to be subject to the government's police power, but this implied limitation cannot swallow the constitutional protections against uncompensated takings entirely.
- The Court identified the size of a regulation's economic impact as a key factor: when a law destroys enough of a property's value, the government must use its formal condemnation power and pay for it, rather than regulating the value away for free.
- Applying this, the Court reasoned that since the value of a coal reservation lies entirely in the ability to mine it profitably, a law making that mining commercially impossible has nearly the same effect as physically destroying the coal itself.
- The Court distinguished an earlier case, Plymouth Coal Co. v. Pennsylvania, where a similar mining restriction was upheld because it protected the safety of mine workers on both sides of a property line and gave each side a matching benefit; here, the coal company received no such matching benefit.
- Because the public and the homeowners had only purchased surface rights while the company kept its coal rights by contract, the Court reasoned that forcing the company to leave support in place for free would give the public more than it had originally paid for.
- Weighing the limited public interest in protecting one private house — a danger the Court thought could be handled by notice — against the near-total loss of the company's coal estate, the Court concluded the law crossed the line from ordinary regulation into an uncompensated taking.
Doctrinal impact
Cases affected by this decision
Distinguishes Plymouth Coal Co. v. Pennsylvania (232 U.S. 531)
Distinguished as a worker-safety rule with mutual benefits, unlike the one-sided burden here.
Distinguishes Block v. Hirsh (256 U.S. 135)
Wartime housing emergency laws with compensation went far but still fell short of this statute.