260 U.S. 393 (1922)
Pennsylvania Coal Co. v.
Does a statute that significantly diminishes the value of private property or impedes certain contractual rights constitute a 'taking' under the Fifth Amendment, such that just compensation is required?
The rule established by the Court is that while property may be regulated to a certain extent, if regulation goes too far it will be recognized as a taking.
The U.S. Supreme Court held that the Kohler Act, by completely prohibiting mining operations under Mahon's property, went too far and constituted a regulatory taking for which Pennsylvania Coal Co. was owed just compensation.
Pennsylvania Coal Co. v. Mahon is significant as it articulated the first clear judicial definition of regulatory takings, shaping future jurisprudence where government regulations affect the economic value of private property. It established the principle that regulations, not just physical appropriations, could amount to takings if they excessively curtail property use, thus mandating compensation. This case laid the groundwork for the 'too far' standard, a crucial measure for realizing a taking under regulatory frameworks it continues to influence land use and environmental law.