480 U.S. 470 (1987), argued 10 Nov. 1986, decided 9 Mar. 1987 by vote of 5 to 4; Stevens for the Court, Rehnquist in dissent. In Keystone, a divided Court upheld a Pennsylvania mining‐subsidence statute against a claim that the statute effected a taking of private property without payment of just compensation. The challenged statute prohibited all underground mining that caused subsidence damage to surface structures, and it obligated mining companies to leave in place, for structural support, at least half of the coal that underlay a protected structure. The Court upheld the statute as a valid exercise of the state's police power, noting that the statute substantially advanced public interests in health, safety, and welfare and did not render the mining companies unable to mine at a profit.
In Keystone the Court continued its prior refusal to divide property parcels into components when determining whether the state had taken property. The Court denied that the small amount of coal left in place for surface support was a discrete property interest that the Pennsylvania statute had, in effect, taken without compensation.
Keystone is remarkable because the facts of the case were virtually identical to those of Pennsylvania Coal Co. v. Mahon (1922), a landmark of takings jurisprudence. In Mahon a state statute prohibited an owner from engaging in underground mining if the mining caused structural subsidence. The Court in Mahon struck down this statute as a taking because the statute served private interests and denied the mining company all economically viable use of the underlying coal. In Keystone, the Court appreciated the public nature of the harms caused by land subsidence; the Court viewed the new statute as one that furthered public interests, not private ones, and it saw land subsidence as a public nuisance.
See also Eminent Domain; Property Rights; Takings Clause.
— Eric T. Freyfogle
