Started the doctrine of regulatory taking, the Pennsylvania Coal Co. granted to H.J. Mahon the surface rights to a parcel of land, but retained the mining rights to the land,. The Kohler Act prohibited the mining of anthracite coal in such way as to cause the subsidence of, among other things, any structure used as a human habitation. Pennsylvania Coal provided notice to Mahon that it planned to mine for coal under the Mahon's habitation and Mahon brought suit to prevent Pennsylvania Coal from mining under his land pursuant to the Kohler Act. The Court ruled that whether a regulatory act constitutes a taking requiring compensation depends on the extent of diminution in the value of the property. The damage done by the activity prohibited by the act is a private, not a public nuisance; there is no public safety justification for the statute, as notice before mining would suffice to protect public safety. he statute, in general, purports to extinguish the mining rights to valuable properties under surfaces owned by the public and the government. The statute makes prohibitively expensive the mining of coal in these areas, and thereby effectively destroys the right, after all owning coal is not worth anything if the coal cannot be mined.