The highest court in Pennsylvania, heart of the country's natural gas drilling boom, on Thursday struck down significant portions of a law that limited the power of local governments to determine where the industry can operate _ rules the industry sought from Republican Gov. Tom Corbett and lawmakers.

In a 4-2 decision, the Pennsylvania Supreme Court ruled the industry-friendly rules set out by the 2012 law violated the state constitution, although the majority did not entirely agree on why they were unconstitutional.

Seven municipalities had challenged the law that grew out of the state's need to modernize 20-year-old drilling laws to account for a Marcellus Shale drilling boom made possible by innovations in technology, most notably horizontal drilling and hydraulic fracturing. The process, also called fracking, has drawn widespread criticism from environmentalists and many residents living near drilling operations.

"Few could seriously dispute how remarkable a revolution is worked by this legislation upon the existing zoning regimen in Pennsylvania, including residential zones," wrote Chief Justice Ron Castille. He said the law's rules represented an unprecedented "displacement of prior planning, and derivative expectations, regarding land use, zoning, and enjoyment of property."

The high court's decision comes at a time when the energy industry is increasingly able to capture oil and gas from previously unreachable formations and, as a result, is bumping up against suburban and urban expectations of land use in states including Texas, Colorado and Ohio, where a similar legal challenge is underway.

The 2012 law restricted local municipalities' ability to control where companies may place rigs, waste pits, pipelines and compressor and processing stations, although the new zoning rules never went into effect because of court order after the towns sued. A narrowly divided lower court struck them down in 2012, but Corbett appealed, saying lawmakers have clear authority to override local zoning.