HARRISBURG - Pennsylvania's highest court has upheld a decision to throw out a state rule that required coal-fired power plants to cut mercury emissions beyond federal standards.

The Supreme Court ruled Wednesday that Commonwealth Court Judge Dan Pellegrini was correct when he called the rule unlawful, invalid, and unenforceable.

The 2007 rule was challenged by Allentown-based PPL Corp., which owns two coal-fired power plants in Pennsylvania.

The governor's office fought industry resistance for approval of the rule, which made Pennsylvania the first major coal-mining state to attack mercury.

Last year, however, a federal judge required mercury to be restored to a list of hazardous pollutants that Pennsylvania state law prohibits it from regulating.