An introduction to Constitutional Law 100 Supreme Court cases everyone should know

Randy E. Barnett & Josh Blackman

In Pennsylvania Coal Company v. Mahon (1922), the Supreme Court attempted to draw the line between a permissible exercise of the police power and an unconstitutional regulatory taking.

Sometimes when coal is mined below the surface, the ground above the surface may collapse. As a result, structures above the surface may sink into the ground. This process is known as “subsidence.” In 1921, Pennsylvania enacted the Kohler Act. The law 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.”

Mahon owned the surface rights to a piece of land.

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